diff mbox series

[RFC,v5,4/4] cpus: extract out accel-specific code to each accel

Message ID 20200615180346.3992-5-cfontana@suse.de
State New
Headers show
Series QEMU cpus.c refactoring | expand

Commit Message

Claudio Fontana June 15, 2020, 6:03 p.m. UTC
each accelerator registers a new "CpusAccel" interface
implementation on initialization, providing functions for
starting a vcpu, kicking a vcpu, and sychronizing state.

This way the code in cpus.c is now all general softmmu code,
nothing accelerator-specific anymore.

There is still some ifdeffery for WIN32 though.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
---
 MAINTAINERS                   |   1 +
 accel/Makefile.objs           |   2 +-
 accel/kvm/Makefile.objs       |   2 +
 accel/kvm/kvm-all.c           |  15 +-
 accel/kvm/kvm-cpus.c          |  94 +++++
 accel/kvm/kvm-cpus.h          |  17 +
 accel/qtest/Makefile.objs     |   2 +
 accel/qtest/qtest-cpus.c      | 105 +++++
 accel/qtest/qtest-cpus.h      |  17 +
 accel/{ => qtest}/qtest.c     |   7 +
 accel/stubs/kvm-stub.c        |   3 +-
 accel/tcg/Makefile.objs       |   1 +
 accel/tcg/tcg-all.c           |  12 +-
 accel/tcg/tcg-cpus.c          | 523 ++++++++++++++++++++++++
 accel/tcg/tcg-cpus.h          |  17 +
 hw/core/cpu.c                 |   1 +
 include/sysemu/cpus.h         |  32 ++
 include/sysemu/hw_accel.h     |  57 +--
 include/sysemu/kvm.h          |   2 +-
 softmmu/cpus.c                | 911 ++++--------------------------------------
 stubs/Makefile.objs           |   1 +
 stubs/cpu-synchronize-state.c |  15 +
 target/i386/Makefile.objs     |   7 +-
 target/i386/hax-all.c         |   6 +-
 target/i386/hax-cpus.c        |  85 ++++
 target/i386/hax-cpus.h        |  17 +
 target/i386/hax-i386.h        |   2 +
 target/i386/hax-posix.c       |  12 +
 target/i386/hax-windows.c     |  20 +
 target/i386/hvf/Makefile.objs |   2 +-
 target/i386/hvf/hvf-cpus.c    | 141 +++++++
 target/i386/hvf/hvf-cpus.h    |  17 +
 target/i386/hvf/hvf.c         |   3 +
 target/i386/whpx-all.c        |   3 +
 target/i386/whpx-cpus.c       |  96 +++++
 target/i386/whpx-cpus.h       |  17 +
 36 files changed, 1362 insertions(+), 903 deletions(-)
 create mode 100644 accel/kvm/kvm-cpus.c
 create mode 100644 accel/kvm/kvm-cpus.h
 create mode 100644 accel/qtest/Makefile.objs
 create mode 100644 accel/qtest/qtest-cpus.c
 create mode 100644 accel/qtest/qtest-cpus.h
 rename accel/{ => qtest}/qtest.c (86%)
 create mode 100644 accel/tcg/tcg-cpus.c
 create mode 100644 accel/tcg/tcg-cpus.h
 create mode 100644 stubs/cpu-synchronize-state.c
 create mode 100644 target/i386/hax-cpus.c
 create mode 100644 target/i386/hax-cpus.h
 create mode 100644 target/i386/hvf/hvf-cpus.c
 create mode 100644 target/i386/hvf/hvf-cpus.h
 create mode 100644 target/i386/whpx-cpus.c
 create mode 100644 target/i386/whpx-cpus.h

Comments

Alex Bennée June 16, 2020, 2:16 p.m. UTC | #1
Claudio Fontana <cfontana@suse.de> writes:

> each accelerator registers a new "CpusAccel" interface
> implementation on initialization, providing functions for
> starting a vcpu, kicking a vcpu, and sychronizing state.
>
> This way the code in cpus.c is now all general softmmu code,
> nothing accelerator-specific anymore.
>
> There is still some ifdeffery for WIN32 though.
>
> Signed-off-by: Claudio Fontana <cfontana@suse.de>
> ---
>  MAINTAINERS                   |   1 +
>  accel/Makefile.objs           |   2 +-
>  accel/kvm/Makefile.objs       |   2 +
>  accel/kvm/kvm-all.c           |  15 +-
>  accel/kvm/kvm-cpus.c          |  94 +++++
>  accel/kvm/kvm-cpus.h          |  17 +
>  accel/qtest/Makefile.objs     |   2 +
>  accel/qtest/qtest-cpus.c      | 105 +++++
>  accel/qtest/qtest-cpus.h      |  17 +
>  accel/{ => qtest}/qtest.c     |   7 +
>  accel/stubs/kvm-stub.c        |   3 +-
>  accel/tcg/Makefile.objs       |   1 +
>  accel/tcg/tcg-all.c           |  12 +-
>  accel/tcg/tcg-cpus.c          | 523 ++++++++++++++++++++++++
>  accel/tcg/tcg-cpus.h          |  17 +
>  hw/core/cpu.c                 |   1 +
>  include/sysemu/cpus.h         |  32 ++
>  include/sysemu/hw_accel.h     |  57 +--
>  include/sysemu/kvm.h          |   2 +-
>  softmmu/cpus.c                | 911 ++++--------------------------------------
>  stubs/Makefile.objs           |   1 +
>  stubs/cpu-synchronize-state.c |  15 +
>  target/i386/Makefile.objs     |   7 +-
>  target/i386/hax-all.c         |   6 +-
>  target/i386/hax-cpus.c        |  85 ++++
>  target/i386/hax-cpus.h        |  17 +
>  target/i386/hax-i386.h        |   2 +
>  target/i386/hax-posix.c       |  12 +
>  target/i386/hax-windows.c     |  20 +
>  target/i386/hvf/Makefile.objs |   2 +-
>  target/i386/hvf/hvf-cpus.c    | 141 +++++++
>  target/i386/hvf/hvf-cpus.h    |  17 +
>  target/i386/hvf/hvf.c         |   3 +
>  target/i386/whpx-all.c        |   3 +
>  target/i386/whpx-cpus.c       |  96 +++++
>  target/i386/whpx-cpus.h       |  17 +
>  36 files changed, 1362 insertions(+), 903 deletions(-)
>  create mode 100644 accel/kvm/kvm-cpus.c
>  create mode 100644 accel/kvm/kvm-cpus.h
>  create mode 100644 accel/qtest/Makefile.objs
>  create mode 100644 accel/qtest/qtest-cpus.c
>  create mode 100644 accel/qtest/qtest-cpus.h
>  rename accel/{ => qtest}/qtest.c (86%)
>  create mode 100644 accel/tcg/tcg-cpus.c
>  create mode 100644 accel/tcg/tcg-cpus.h
>  create mode 100644 stubs/cpu-synchronize-state.c
>  create mode 100644 target/i386/hax-cpus.c
>  create mode 100644 target/i386/hax-cpus.h
>  create mode 100644 target/i386/hvf/hvf-cpus.c
>  create mode 100644 target/i386/hvf/hvf-cpus.h
>  create mode 100644 target/i386/whpx-cpus.c
>  create mode 100644 target/i386/whpx-cpus.h

Predictably for such a spider patch I got a bunch of conflicts
attempting to merge on my testing branch so only a few comments.

>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f308537d42..ef8cbb2680 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -427,6 +427,7 @@ WHPX CPUs
>  M: Sunil Muthuswamy <sunilmut@microsoft.com>
>  S: Supported
>  F: target/i386/whpx-all.c
> +F: target/i386/whpx-cpus.c
>  F: target/i386/whp-dispatch.h
>  F: accel/stubs/whpx-stub.c
>  F: include/sysemu/whpx.h
> diff --git a/accel/Makefile.objs b/accel/Makefile.objs
> index ff72f0d030..c5e58eb53d 100644
> --- a/accel/Makefile.objs
> +++ b/accel/Makefile.objs
> @@ -1,5 +1,5 @@
>  common-obj-$(CONFIG_SOFTMMU) += accel.o
> -obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o
> +obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/

This does raise the question if qtest is "just another" accelerator then
should we not be creating a CONFIG_QTEST symbol for explicitness?

>  obj-$(CONFIG_KVM) += kvm/
>  obj-$(CONFIG_TCG) += tcg/
>  obj-$(CONFIG_XEN) += xen/
<snip>
> +static void *qtest_cpu_thread_fn(void *arg)
> +{
> +#ifdef _WIN32
> +    error_report("qtest is not supported under Windows");
> +    exit(1);
> +#else

This is literally impossible to build isn't it?
>  
>  static int qtest_init_accel(MachineState *ms)
>  {
> +    cpus_register_accel(&qtest_cpus);
>      return 0;
>  }

I wonder if these register functions could be moved to initfns like we
use for our hardware models?

<snip>
>  
> +/*
> + * every accelerator is supposed to register this.
> + * Could be in the AccelClass instead, but ends up being too complicated
> + * to access in practice, and inefficient for each call of each method.
> + */
> +static CpusAccel cpus_accel;
> +

wait what? Does an indirection cause that much trouble? I'm surprised
given how often we use it elsewhere in the code. I guess others might
argue for a full QOM-ification of the accelerator but I think we can at
least have an indirection rather than a copy of the structure.
Claudio Fontana June 16, 2020, 5:01 p.m. UTC | #2
Hi Alex,

thanks for looking at this,

On 6/16/20 4:16 PM, Alex Bennée wrote:
> 
> Claudio Fontana <cfontana@suse.de> writes:
> 
>> each accelerator registers a new "CpusAccel" interface
>> implementation on initialization, providing functions for
>> starting a vcpu, kicking a vcpu, and sychronizing state.
>>
>> This way the code in cpus.c is now all general softmmu code,
>> nothing accelerator-specific anymore.
>>
>> There is still some ifdeffery for WIN32 though.
>>
>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>> ---
>>  MAINTAINERS                   |   1 +
>>  accel/Makefile.objs           |   2 +-
>>  accel/kvm/Makefile.objs       |   2 +
>>  accel/kvm/kvm-all.c           |  15 +-
>>  accel/kvm/kvm-cpus.c          |  94 +++++
>>  accel/kvm/kvm-cpus.h          |  17 +
>>  accel/qtest/Makefile.objs     |   2 +
>>  accel/qtest/qtest-cpus.c      | 105 +++++
>>  accel/qtest/qtest-cpus.h      |  17 +
>>  accel/{ => qtest}/qtest.c     |   7 +
>>  accel/stubs/kvm-stub.c        |   3 +-
>>  accel/tcg/Makefile.objs       |   1 +
>>  accel/tcg/tcg-all.c           |  12 +-
>>  accel/tcg/tcg-cpus.c          | 523 ++++++++++++++++++++++++
>>  accel/tcg/tcg-cpus.h          |  17 +
>>  hw/core/cpu.c                 |   1 +
>>  include/sysemu/cpus.h         |  32 ++
>>  include/sysemu/hw_accel.h     |  57 +--
>>  include/sysemu/kvm.h          |   2 +-
>>  softmmu/cpus.c                | 911 ++++--------------------------------------
>>  stubs/Makefile.objs           |   1 +
>>  stubs/cpu-synchronize-state.c |  15 +
>>  target/i386/Makefile.objs     |   7 +-
>>  target/i386/hax-all.c         |   6 +-
>>  target/i386/hax-cpus.c        |  85 ++++
>>  target/i386/hax-cpus.h        |  17 +
>>  target/i386/hax-i386.h        |   2 +
>>  target/i386/hax-posix.c       |  12 +
>>  target/i386/hax-windows.c     |  20 +
>>  target/i386/hvf/Makefile.objs |   2 +-
>>  target/i386/hvf/hvf-cpus.c    | 141 +++++++
>>  target/i386/hvf/hvf-cpus.h    |  17 +
>>  target/i386/hvf/hvf.c         |   3 +
>>  target/i386/whpx-all.c        |   3 +
>>  target/i386/whpx-cpus.c       |  96 +++++
>>  target/i386/whpx-cpus.h       |  17 +
>>  36 files changed, 1362 insertions(+), 903 deletions(-)
>>  create mode 100644 accel/kvm/kvm-cpus.c
>>  create mode 100644 accel/kvm/kvm-cpus.h
>>  create mode 100644 accel/qtest/Makefile.objs
>>  create mode 100644 accel/qtest/qtest-cpus.c
>>  create mode 100644 accel/qtest/qtest-cpus.h
>>  rename accel/{ => qtest}/qtest.c (86%)
>>  create mode 100644 accel/tcg/tcg-cpus.c
>>  create mode 100644 accel/tcg/tcg-cpus.h
>>  create mode 100644 stubs/cpu-synchronize-state.c
>>  create mode 100644 target/i386/hax-cpus.c
>>  create mode 100644 target/i386/hax-cpus.h
>>  create mode 100644 target/i386/hvf/hvf-cpus.c
>>  create mode 100644 target/i386/hvf/hvf-cpus.h
>>  create mode 100644 target/i386/whpx-cpus.c
>>  create mode 100644 target/i386/whpx-cpus.h
> 
> Predictably for such a spider patch I got a bunch of conflicts
> attempting to merge on my testing branch so only a few comments.
> 
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index f308537d42..ef8cbb2680 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -427,6 +427,7 @@ WHPX CPUs
>>  M: Sunil Muthuswamy <sunilmut@microsoft.com>
>>  S: Supported
>>  F: target/i386/whpx-all.c
>> +F: target/i386/whpx-cpus.c
>>  F: target/i386/whp-dispatch.h
>>  F: accel/stubs/whpx-stub.c
>>  F: include/sysemu/whpx.h
>> diff --git a/accel/Makefile.objs b/accel/Makefile.objs
>> index ff72f0d030..c5e58eb53d 100644
>> --- a/accel/Makefile.objs
>> +++ b/accel/Makefile.objs
>> @@ -1,5 +1,5 @@
>>  common-obj-$(CONFIG_SOFTMMU) += accel.o
>> -obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o
>> +obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/
> 
> This does raise the question if qtest is "just another" accelerator then
> should we not be creating a CONFIG_QTEST symbol for explicitness?
> 
>>  obj-$(CONFIG_KVM) += kvm/
>>  obj-$(CONFIG_TCG) += tcg/
>>  obj-$(CONFIG_XEN) += xen/
> <snip>
>> +static void *qtest_cpu_thread_fn(void *arg)
>> +{
>> +#ifdef _WIN32
>> +    error_report("qtest is not supported under Windows");
>> +    exit(1);
>> +#else
> 
> This is literally impossible to build isn't it?
>>  
>>  static int qtest_init_accel(MachineState *ms)
>>  {
>> +    cpus_register_accel(&qtest_cpus);
>>      return 0;
>>  }
> 
> I wonder if these register functions could be moved to initfns like we
> use for our hardware models?

The context is the configure_accelerator() in vl.c , where we loop over possible candidate accelerators
and try to initialize them.

In this RFC the cpus_register_accel is triggered at accel_init_machine() time,
in the accelerator class init_machine() method, where we are trying to use a specific accelerator.

This is the case for qtest like for the other AccelClass types (tcg and the hardware accelerators).

If not in init_machine(), where would the registration best happen?

> 
> <snip>
>>  
>> +/*
>> + * every accelerator is supposed to register this.
>> + * Could be in the AccelClass instead, but ends up being too complicated
>> + * to access in practice, and inefficient for each call of each method.
>> + */
>> +static CpusAccel cpus_accel;
>> +
> 
> wait what? Does an indirection cause that much trouble? I'm surprised
> given how often we use it elsewhere in the code. I guess others might

CpusAccel is not used elsewhere currently in the codebase, it's new, or what do you mean?

> argue for a full QOM-ification of the accelerator but I think we can at
> least have an indirection rather than a copy of the structure.
> 
> 

As mentioned in v3 and v2, this is what we end up if we put CpusAccel inside the AccelClass,
every time we need a vcpu kick, sync state, etc:

1) current_accel() function call
2) pointer dereference (->accelerator)
3) object_class_dynamic_cast_assert function call (ACCEL_GET_CLASS -> OBJECT_CLASS_CHECK)
4) pointer dereference (-> AccelCpusInterface)
5) pointer dereference (-> method)
6) function call ( ->synchronize_state(cpu))

So the code then would look like this (more or less, probably I would put also an assert for non-NULL in there):

VERSION A)

void cpu_synchronize_state(CPUState *cpu)
{
    ACCEL_GET_CLASS(current_accel())->cpus_int->synchronize_state(cpu);
}

Instead with the current RFC code, this is what we end up with every time we need a vcpu kick, sync state, etc:

VERSION B)

void cpu_synchronize_state(CPUState *cpu)
{
    cpus_accel.synchronize_state(cpu);
}


Are you arguing in favor of VERSION A) here?

I would like to have an ACK from the owners of the hardware accels especially that the additional overhead in this code path
is of negligible importance..


Thank you for your comments,

Ciao,

Claudio
Alex Bennée June 16, 2020, 5:52 p.m. UTC | #3
Claudio Fontana <cfontana@suse.de> writes:

> Hi Alex,
>
> thanks for looking at this,
>
> On 6/16/20 4:16 PM, Alex Bennée wrote:
>> 
>> Claudio Fontana <cfontana@suse.de> writes:
>> 
>>> each accelerator registers a new "CpusAccel" interface
>>> implementation on initialization, providing functions for
>>> starting a vcpu, kicking a vcpu, and sychronizing state.
>>>
>>> This way the code in cpus.c is now all general softmmu code,
>>> nothing accelerator-specific anymore.
>>>
>>> There is still some ifdeffery for WIN32 though.
>>>
>>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>>> ---
>>>  MAINTAINERS                   |   1 +
>>>  accel/Makefile.objs           |   2 +-
>>>  accel/kvm/Makefile.objs       |   2 +
>>>  accel/kvm/kvm-all.c           |  15 +-
>>>  accel/kvm/kvm-cpus.c          |  94 +++++
>>>  accel/kvm/kvm-cpus.h          |  17 +
>>>  accel/qtest/Makefile.objs     |   2 +
>>>  accel/qtest/qtest-cpus.c      | 105 +++++
>>>  accel/qtest/qtest-cpus.h      |  17 +
>>>  accel/{ => qtest}/qtest.c     |   7 +
>>>  accel/stubs/kvm-stub.c        |   3 +-
>>>  accel/tcg/Makefile.objs       |   1 +
>>>  accel/tcg/tcg-all.c           |  12 +-
>>>  accel/tcg/tcg-cpus.c          | 523 ++++++++++++++++++++++++
>>>  accel/tcg/tcg-cpus.h          |  17 +
>>>  hw/core/cpu.c                 |   1 +
>>>  include/sysemu/cpus.h         |  32 ++
>>>  include/sysemu/hw_accel.h     |  57 +--
>>>  include/sysemu/kvm.h          |   2 +-
>>>  softmmu/cpus.c                | 911 ++++--------------------------------------
>>>  stubs/Makefile.objs           |   1 +
>>>  stubs/cpu-synchronize-state.c |  15 +
>>>  target/i386/Makefile.objs     |   7 +-
>>>  target/i386/hax-all.c         |   6 +-
>>>  target/i386/hax-cpus.c        |  85 ++++
>>>  target/i386/hax-cpus.h        |  17 +
>>>  target/i386/hax-i386.h        |   2 +
>>>  target/i386/hax-posix.c       |  12 +
>>>  target/i386/hax-windows.c     |  20 +
>>>  target/i386/hvf/Makefile.objs |   2 +-
>>>  target/i386/hvf/hvf-cpus.c    | 141 +++++++
>>>  target/i386/hvf/hvf-cpus.h    |  17 +
>>>  target/i386/hvf/hvf.c         |   3 +
>>>  target/i386/whpx-all.c        |   3 +
>>>  target/i386/whpx-cpus.c       |  96 +++++
>>>  target/i386/whpx-cpus.h       |  17 +
>>>  36 files changed, 1362 insertions(+), 903 deletions(-)
>>>  create mode 100644 accel/kvm/kvm-cpus.c
>>>  create mode 100644 accel/kvm/kvm-cpus.h
>>>  create mode 100644 accel/qtest/Makefile.objs
>>>  create mode 100644 accel/qtest/qtest-cpus.c
>>>  create mode 100644 accel/qtest/qtest-cpus.h
>>>  rename accel/{ => qtest}/qtest.c (86%)
>>>  create mode 100644 accel/tcg/tcg-cpus.c
>>>  create mode 100644 accel/tcg/tcg-cpus.h
>>>  create mode 100644 stubs/cpu-synchronize-state.c
>>>  create mode 100644 target/i386/hax-cpus.c
>>>  create mode 100644 target/i386/hax-cpus.h
>>>  create mode 100644 target/i386/hvf/hvf-cpus.c
>>>  create mode 100644 target/i386/hvf/hvf-cpus.h
>>>  create mode 100644 target/i386/whpx-cpus.c
>>>  create mode 100644 target/i386/whpx-cpus.h
>> 
>> Predictably for such a spider patch I got a bunch of conflicts
>> attempting to merge on my testing branch so only a few comments.
>> 
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index f308537d42..ef8cbb2680 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -427,6 +427,7 @@ WHPX CPUs
>>>  M: Sunil Muthuswamy <sunilmut@microsoft.com>
>>>  S: Supported
>>>  F: target/i386/whpx-all.c
>>> +F: target/i386/whpx-cpus.c
>>>  F: target/i386/whp-dispatch.h
>>>  F: accel/stubs/whpx-stub.c
>>>  F: include/sysemu/whpx.h
>>> diff --git a/accel/Makefile.objs b/accel/Makefile.objs
>>> index ff72f0d030..c5e58eb53d 100644
>>> --- a/accel/Makefile.objs
>>> +++ b/accel/Makefile.objs
>>> @@ -1,5 +1,5 @@
>>>  common-obj-$(CONFIG_SOFTMMU) += accel.o
>>> -obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o
>>> +obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/
>> 
>> This does raise the question if qtest is "just another" accelerator then
>> should we not be creating a CONFIG_QTEST symbol for explicitness?
>> 
>>>  obj-$(CONFIG_KVM) += kvm/
>>>  obj-$(CONFIG_TCG) += tcg/
>>>  obj-$(CONFIG_XEN) += xen/
>> <snip>
>>> +static void *qtest_cpu_thread_fn(void *arg)
>>> +{
>>> +#ifdef _WIN32
>>> +    error_report("qtest is not supported under Windows");
>>> +    exit(1);
>>> +#else
>> 
>> This is literally impossible to build isn't it?
>>>  
>>>  static int qtest_init_accel(MachineState *ms)
>>>  {
>>> +    cpus_register_accel(&qtest_cpus);
>>>      return 0;
>>>  }
>> 
>> I wonder if these register functions could be moved to initfns like we
>> use for our hardware models?
>
> The context is the configure_accelerator() in vl.c , where we loop over possible candidate accelerators
> and try to initialize them.
>
> In this RFC the cpus_register_accel is triggered at accel_init_machine() time,
> in the accelerator class init_machine() method, where we are trying to use a specific accelerator.
>
> This is the case for qtest like for the other AccelClass types (tcg and the hardware accelerators).
>
> If not in init_machine(), where would the registration best happen?

Ahh I see - this is once the decision about which accelerator has been
made. I was thinking along the lines of the init functions driven by:

  #define type_init(function) module_init(function, MODULE_INIT_QOM)

which would then populate the list of available accelerators in a more
QOM like manner. I assume having a completely configurable set of
accelerators is the eventual aim of this?

>
>> 
>> <snip>
>>>  
>>> +/*
>>> + * every accelerator is supposed to register this.
>>> + * Could be in the AccelClass instead, but ends up being too complicated
>>> + * to access in practice, and inefficient for each call of each method.
>>> + */
>>> +static CpusAccel cpus_accel;
>>> +
>> 
>> wait what? Does an indirection cause that much trouble? I'm surprised
>> given how often we use it elsewhere in the code. I guess others might
>
> CpusAccel is not used elsewhere currently in the codebase, it's new, or what do you mean?
>
>> argue for a full QOM-ification of the accelerator but I think we can at
>> least have an indirection rather than a copy of the structure.
>> 
>> 
>
> As mentioned in v3 and v2, this is what we end up if we put CpusAccel inside the AccelClass,
> every time we need a vcpu kick, sync state, etc:
>
> 1) current_accel() function call
> 2) pointer dereference (->accelerator)
> 3) object_class_dynamic_cast_assert function call (ACCEL_GET_CLASS -> OBJECT_CLASS_CHECK)
> 4) pointer dereference (-> AccelCpusInterface)
> 5) pointer dereference (-> method)
> 6) function call ( ->synchronize_state(cpu))
>
> So the code then would look like this (more or less, probably I would put also an assert for non-NULL in there):
>
> VERSION A)
>
> void cpu_synchronize_state(CPUState *cpu)
> {
>     ACCEL_GET_CLASS(current_accel())->cpus_int->synchronize_state(cpu);
> }

I don't think it has to be quite so extreme. I was just arguing for
something along the lines of:

static CpuAccel *accel;

and

void cpu_synchronize_state(CPUState *cpu)
{
   if (accel && accel->synchronize_state) {
      accel->synchronize_state(cpu);
   }
}

> Instead with the current RFC code, this is what we end up with every
> time we need a vcpu kick, sync state, etc:

I don't think a pointer de-reference alone is super critical for
something that happens on the outside of the main run loop. It might be
a different argument if this was somewhere in the hot path.

> Are you arguing in favor of VERSION A) here?

Version C ;-)

>
> I would like to have an ACK from the owners of the hardware accels especially that the additional overhead in this code path
> is of negligible importance..
>
>
> Thank you for your comments,
>
> Ciao,
>
> Claudio
Claudio Fontana June 16, 2020, 6:02 p.m. UTC | #4
On 6/16/20 7:52 PM, Alex Bennée wrote:
> 
> Claudio Fontana <cfontana@suse.de> writes:
> 
>> Hi Alex,
>>
>> thanks for looking at this,
>>
>> On 6/16/20 4:16 PM, Alex Bennée wrote:
>>>
>>> Claudio Fontana <cfontana@suse.de> writes:
>>>
>>>> each accelerator registers a new "CpusAccel" interface
>>>> implementation on initialization, providing functions for
>>>> starting a vcpu, kicking a vcpu, and sychronizing state.
>>>>
>>>> This way the code in cpus.c is now all general softmmu code,
>>>> nothing accelerator-specific anymore.
>>>>
>>>> There is still some ifdeffery for WIN32 though.
>>>>
>>>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>>>> ---
>>>>  MAINTAINERS                   |   1 +
>>>>  accel/Makefile.objs           |   2 +-
>>>>  accel/kvm/Makefile.objs       |   2 +
>>>>  accel/kvm/kvm-all.c           |  15 +-
>>>>  accel/kvm/kvm-cpus.c          |  94 +++++
>>>>  accel/kvm/kvm-cpus.h          |  17 +
>>>>  accel/qtest/Makefile.objs     |   2 +
>>>>  accel/qtest/qtest-cpus.c      | 105 +++++
>>>>  accel/qtest/qtest-cpus.h      |  17 +
>>>>  accel/{ => qtest}/qtest.c     |   7 +
>>>>  accel/stubs/kvm-stub.c        |   3 +-
>>>>  accel/tcg/Makefile.objs       |   1 +
>>>>  accel/tcg/tcg-all.c           |  12 +-
>>>>  accel/tcg/tcg-cpus.c          | 523 ++++++++++++++++++++++++
>>>>  accel/tcg/tcg-cpus.h          |  17 +
>>>>  hw/core/cpu.c                 |   1 +
>>>>  include/sysemu/cpus.h         |  32 ++
>>>>  include/sysemu/hw_accel.h     |  57 +--
>>>>  include/sysemu/kvm.h          |   2 +-
>>>>  softmmu/cpus.c                | 911 ++++--------------------------------------
>>>>  stubs/Makefile.objs           |   1 +
>>>>  stubs/cpu-synchronize-state.c |  15 +
>>>>  target/i386/Makefile.objs     |   7 +-
>>>>  target/i386/hax-all.c         |   6 +-
>>>>  target/i386/hax-cpus.c        |  85 ++++
>>>>  target/i386/hax-cpus.h        |  17 +
>>>>  target/i386/hax-i386.h        |   2 +
>>>>  target/i386/hax-posix.c       |  12 +
>>>>  target/i386/hax-windows.c     |  20 +
>>>>  target/i386/hvf/Makefile.objs |   2 +-
>>>>  target/i386/hvf/hvf-cpus.c    | 141 +++++++
>>>>  target/i386/hvf/hvf-cpus.h    |  17 +
>>>>  target/i386/hvf/hvf.c         |   3 +
>>>>  target/i386/whpx-all.c        |   3 +
>>>>  target/i386/whpx-cpus.c       |  96 +++++
>>>>  target/i386/whpx-cpus.h       |  17 +
>>>>  36 files changed, 1362 insertions(+), 903 deletions(-)
>>>>  create mode 100644 accel/kvm/kvm-cpus.c
>>>>  create mode 100644 accel/kvm/kvm-cpus.h
>>>>  create mode 100644 accel/qtest/Makefile.objs
>>>>  create mode 100644 accel/qtest/qtest-cpus.c
>>>>  create mode 100644 accel/qtest/qtest-cpus.h
>>>>  rename accel/{ => qtest}/qtest.c (86%)
>>>>  create mode 100644 accel/tcg/tcg-cpus.c
>>>>  create mode 100644 accel/tcg/tcg-cpus.h
>>>>  create mode 100644 stubs/cpu-synchronize-state.c
>>>>  create mode 100644 target/i386/hax-cpus.c
>>>>  create mode 100644 target/i386/hax-cpus.h
>>>>  create mode 100644 target/i386/hvf/hvf-cpus.c
>>>>  create mode 100644 target/i386/hvf/hvf-cpus.h
>>>>  create mode 100644 target/i386/whpx-cpus.c
>>>>  create mode 100644 target/i386/whpx-cpus.h
>>>
>>> Predictably for such a spider patch I got a bunch of conflicts
>>> attempting to merge on my testing branch so only a few comments.
>>>
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index f308537d42..ef8cbb2680 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -427,6 +427,7 @@ WHPX CPUs
>>>>  M: Sunil Muthuswamy <sunilmut@microsoft.com>
>>>>  S: Supported
>>>>  F: target/i386/whpx-all.c
>>>> +F: target/i386/whpx-cpus.c
>>>>  F: target/i386/whp-dispatch.h
>>>>  F: accel/stubs/whpx-stub.c
>>>>  F: include/sysemu/whpx.h
>>>> diff --git a/accel/Makefile.objs b/accel/Makefile.objs
>>>> index ff72f0d030..c5e58eb53d 100644
>>>> --- a/accel/Makefile.objs
>>>> +++ b/accel/Makefile.objs
>>>> @@ -1,5 +1,5 @@
>>>>  common-obj-$(CONFIG_SOFTMMU) += accel.o
>>>> -obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o
>>>> +obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/
>>>
>>> This does raise the question if qtest is "just another" accelerator then
>>> should we not be creating a CONFIG_QTEST symbol for explicitness?
>>>
>>>>  obj-$(CONFIG_KVM) += kvm/
>>>>  obj-$(CONFIG_TCG) += tcg/
>>>>  obj-$(CONFIG_XEN) += xen/
>>> <snip>
>>>> +static void *qtest_cpu_thread_fn(void *arg)
>>>> +{
>>>> +#ifdef _WIN32
>>>> +    error_report("qtest is not supported under Windows");
>>>> +    exit(1);
>>>> +#else
>>>
>>> This is literally impossible to build isn't it?
>>>>  
>>>>  static int qtest_init_accel(MachineState *ms)
>>>>  {
>>>> +    cpus_register_accel(&qtest_cpus);
>>>>      return 0;
>>>>  }
>>>
>>> I wonder if these register functions could be moved to initfns like we
>>> use for our hardware models?
>>
>> The context is the configure_accelerator() in vl.c , where we loop over possible candidate accelerators
>> and try to initialize them.
>>
>> In this RFC the cpus_register_accel is triggered at accel_init_machine() time,
>> in the accelerator class init_machine() method, where we are trying to use a specific accelerator.
>>
>> This is the case for qtest like for the other AccelClass types (tcg and the hardware accelerators).
>>
>> If not in init_machine(), where would the registration best happen?
> 
> Ahh I see - this is once the decision about which accelerator has been
> made. I was thinking along the lines of the init functions driven by:
> 
>   #define type_init(function) module_init(function, MODULE_INIT_QOM)
> 
> which would then populate the list of available accelerators in a more
> QOM like manner. I assume having a completely configurable set of
> accelerators is the eventual aim of this?


Yes, in my plan the change to add target-specific modules and eventually CONFIG_TCG=m, CONFIG_KVM=m etc is basically the last step, the way I see it.

tentative plan is at:

https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg04628.html


> 
>>
>>>
>>> <snip>
>>>>  
>>>> +/*
>>>> + * every accelerator is supposed to register this.
>>>> + * Could be in the AccelClass instead, but ends up being too complicated
>>>> + * to access in practice, and inefficient for each call of each method.
>>>> + */
>>>> +static CpusAccel cpus_accel;
>>>> +
>>>
>>> wait what? Does an indirection cause that much trouble? I'm surprised
>>> given how often we use it elsewhere in the code. I guess others might
>>
>> CpusAccel is not used elsewhere currently in the codebase, it's new, or what do you mean?
>>
>>> argue for a full QOM-ification of the accelerator but I think we can at
>>> least have an indirection rather than a copy of the structure.
>>>
>>>
>>
>> As mentioned in v3 and v2, this is what we end up if we put CpusAccel inside the AccelClass,
>> every time we need a vcpu kick, sync state, etc:
>>
>> 1) current_accel() function call
>> 2) pointer dereference (->accelerator)
>> 3) object_class_dynamic_cast_assert function call (ACCEL_GET_CLASS -> OBJECT_CLASS_CHECK)
>> 4) pointer dereference (-> AccelCpusInterface)
>> 5) pointer dereference (-> method)
>> 6) function call ( ->synchronize_state(cpu))
>>
>> So the code then would look like this (more or less, probably I would put also an assert for non-NULL in there):
>>
>> VERSION A)
>>
>> void cpu_synchronize_state(CPUState *cpu)
>> {
>>     ACCEL_GET_CLASS(current_accel())->cpus_int->synchronize_state(cpu);
>> }
> 
> I don't think it has to be quite so extreme. I was just arguing for
> something along the lines of:
> 
> static CpuAccel *accel;
> 
> and
> 
> void cpu_synchronize_state(CPUState *cpu)
> {
>    if (accel && accel->synchronize_state) {
>       accel->synchronize_state(cpu);
>    }
> }
> 
>> Instead with the current RFC code, this is what we end up with every
>> time we need a vcpu kick, sync state, etc:
> 
> I don't think a pointer de-reference alone is super critical for
> something that happens on the outside of the main run loop. It might be
> a different argument if this was somewhere in the hot path.
> 
>> Are you arguing in favor of VERSION A) here?
> 
> Version C ;-)

Aha, ok I am comfortable with version C.

> 
>>
>> I would like to have an ACK from the owners of the hardware accels especially that the additional overhead in this code path
>> is of negligible importance..
>>
>>
>> Thank you for your comments,
>>

Ciao,

Claudio
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index f308537d42..ef8cbb2680 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -427,6 +427,7 @@  WHPX CPUs
 M: Sunil Muthuswamy <sunilmut@microsoft.com>
 S: Supported
 F: target/i386/whpx-all.c
+F: target/i386/whpx-cpus.c
 F: target/i386/whp-dispatch.h
 F: accel/stubs/whpx-stub.c
 F: include/sysemu/whpx.h
diff --git a/accel/Makefile.objs b/accel/Makefile.objs
index ff72f0d030..c5e58eb53d 100644
--- a/accel/Makefile.objs
+++ b/accel/Makefile.objs
@@ -1,5 +1,5 @@ 
 common-obj-$(CONFIG_SOFTMMU) += accel.o
-obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest.o
+obj-$(call land,$(CONFIG_SOFTMMU),$(CONFIG_POSIX)) += qtest/
 obj-$(CONFIG_KVM) += kvm/
 obj-$(CONFIG_TCG) += tcg/
 obj-$(CONFIG_XEN) += xen/
diff --git a/accel/kvm/Makefile.objs b/accel/kvm/Makefile.objs
index fdfa481578..ce0f492b8d 100644
--- a/accel/kvm/Makefile.objs
+++ b/accel/kvm/Makefile.objs
@@ -1,2 +1,4 @@ 
 obj-y += kvm-all.o
+obj-y += kvm-cpus.o
+
 obj-$(call lnot,$(CONFIG_SEV)) += sev-stub.o
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index f24d7da783..204385f514 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -45,6 +45,10 @@ 
 #include "qapi/qapi-types-common.h"
 #include "qapi/qapi-visit-common.h"
 #include "sysemu/reset.h"
+#include "qemu/guest-random.h"
+
+#include "sysemu/hw_accel.h"
+#include "kvm-cpus.h"
 
 #include "hw/boards.h"
 
@@ -379,7 +383,7 @@  err:
     return ret;
 }
 
-int kvm_destroy_vcpu(CPUState *cpu)
+static int do_kvm_destroy_vcpu(CPUState *cpu)
 {
     KVMState *s = kvm_state;
     long mmap_size;
@@ -413,6 +417,14 @@  err:
     return ret;
 }
 
+void kvm_destroy_vcpu(CPUState *cpu)
+{
+    if (do_kvm_destroy_vcpu(cpu) < 0) {
+        error_report("kvm_destroy_vcpu failed");
+        exit(EXIT_FAILURE);
+    }
+}
+
 static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id)
 {
     struct KVMParkedVcpu *cpu;
@@ -2225,6 +2237,7 @@  static int kvm_init(MachineState *ms)
         qemu_balloon_inhibit(true);
     }
 
+    cpus_register_accel(&kvm_cpus);
     return 0;
 
 err:
diff --git a/accel/kvm/kvm-cpus.c b/accel/kvm/kvm-cpus.c
new file mode 100644
index 0000000000..ac6945a9e6
--- /dev/null
+++ b/accel/kvm/kvm-cpus.c
@@ -0,0 +1,94 @@ 
+/*
+ * QEMU KVM support
+ *
+ * Copyright IBM, Corp. 2008
+ *           Red Hat, Inc. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Glauber Costa     <gcosta@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+#include "sysemu/kvm_int.h"
+#include "sysemu/runstate.h"
+#include "sysemu/cpus.h"
+#include "qemu/guest-random.h"
+
+#include "kvm-cpus.h"
+
+static void kvm_kick_vcpu_thread(CPUState *cpu)
+{
+    cpus_kick_thread(cpu);
+}
+
+static void *kvm_vcpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+    int r;
+
+    rcu_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+    cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
+    current_cpu = cpu;
+
+    r = kvm_init_vcpu(cpu);
+    if (r < 0) {
+        error_report("kvm_init_vcpu failed: %s", strerror(-r));
+        exit(1);
+    }
+
+    kvm_init_cpu_signals(cpu);
+
+    /* signal CPU creation */
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    do {
+        if (cpu_can_run(cpu)) {
+            r = kvm_cpu_exec(cpu);
+            if (r == EXCP_DEBUG) {
+                cpu_handle_guest_debug(cpu);
+            }
+        }
+        qemu_wait_io_event(cpu);
+    } while (!cpu->unplug || cpu_can_run(cpu));
+
+    kvm_destroy_vcpu(cpu);
+    cpu_thread_signal_destroyed(cpu);
+    qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static void kvm_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+
+    cpu->thread = g_malloc0(sizeof(QemuThread));
+    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(cpu->halt_cond);
+    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/KVM",
+             cpu->cpu_index);
+    qemu_thread_create(cpu->thread, thread_name, kvm_vcpu_thread_fn,
+                       cpu, QEMU_THREAD_JOINABLE);
+}
+
+CpusAccel kvm_cpus = {
+    .create_vcpu_thread = kvm_start_vcpu_thread,
+    .kick_vcpu_thread = kvm_kick_vcpu_thread,
+
+    .synchronize_post_reset = kvm_cpu_synchronize_post_reset,
+    .synchronize_post_init = kvm_cpu_synchronize_post_init,
+    .synchronize_state = kvm_cpu_synchronize_state,
+    .synchronize_pre_loadvm = kvm_cpu_synchronize_pre_loadvm,
+};
diff --git a/accel/kvm/kvm-cpus.h b/accel/kvm/kvm-cpus.h
new file mode 100644
index 0000000000..62fbc911d9
--- /dev/null
+++ b/accel/kvm/kvm-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef KVM_CPUS_H
+#define KVM_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel kvm_cpus;
+
+#endif /* KVM_CPUS_H */
diff --git a/accel/qtest/Makefile.objs b/accel/qtest/Makefile.objs
new file mode 100644
index 0000000000..627014200e
--- /dev/null
+++ b/accel/qtest/Makefile.objs
@@ -0,0 +1,2 @@ 
+obj-y += qtest.o
+obj-y += qtest-cpus.o
diff --git a/accel/qtest/qtest-cpus.c b/accel/qtest/qtest-cpus.c
new file mode 100644
index 0000000000..4f7ace7fff
--- /dev/null
+++ b/accel/qtest/qtest-cpus.c
@@ -0,0 +1,105 @@ 
+/*
+ * QTest accelerator code
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/rcu.h"
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/config-file.h"
+#include "sysemu/accel.h"
+#include "sysemu/qtest.h"
+#include "sysemu/cpus.h"
+#include "sysemu/cpu-timers.h"
+#include "qemu/guest-random.h"
+#include "qemu/main-loop.h"
+#include "hw/core/cpu.h"
+
+#include "qtest-cpus.h"
+
+static void qtest_cpu_synchronize_noop(CPUState *cpu)
+{
+}
+
+static void qtest_kick_vcpu_thread(CPUState *cpu)
+{
+    cpus_kick_thread(cpu);
+}
+
+static void *qtest_cpu_thread_fn(void *arg)
+{
+#ifdef _WIN32
+    error_report("qtest is not supported under Windows");
+    exit(1);
+#else
+    CPUState *cpu = arg;
+    sigset_t waitset;
+    int r;
+
+    rcu_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+    cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
+    current_cpu = cpu;
+
+    sigemptyset(&waitset);
+    sigaddset(&waitset, SIG_IPI);
+
+    /* signal CPU creation */
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    do {
+        qemu_mutex_unlock_iothread();
+        do {
+            int sig;
+            r = sigwait(&waitset, &sig);
+        } while (r == -1 && (errno == EAGAIN || errno == EINTR));
+        if (r == -1) {
+            perror("sigwait");
+            exit(1);
+        }
+        qemu_mutex_lock_iothread();
+        qemu_wait_io_event(cpu);
+    } while (!cpu->unplug);
+
+    qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
+    return NULL;
+#endif
+}
+
+static void qtest_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+
+    cpu->thread = g_malloc0(sizeof(QemuThread));
+    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(cpu->halt_cond);
+    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/DUMMY",
+             cpu->cpu_index);
+    qemu_thread_create(cpu->thread, thread_name, qtest_cpu_thread_fn, cpu,
+                       QEMU_THREAD_JOINABLE);
+}
+
+CpusAccel qtest_cpus = {
+    .create_vcpu_thread = qtest_start_vcpu_thread,
+    .kick_vcpu_thread = qtest_kick_vcpu_thread,
+
+    .synchronize_post_reset = qtest_cpu_synchronize_noop,
+    .synchronize_post_init = qtest_cpu_synchronize_noop,
+    .synchronize_state = qtest_cpu_synchronize_noop,
+    .synchronize_pre_loadvm = qtest_cpu_synchronize_noop,
+};
diff --git a/accel/qtest/qtest-cpus.h b/accel/qtest/qtest-cpus.h
new file mode 100644
index 0000000000..c1fab96b9e
--- /dev/null
+++ b/accel/qtest/qtest-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef QTEST_CPUS_H
+#define QTEST_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel qtest_cpus;
+
+#endif /* QTEST_CPUS_H */
diff --git a/accel/qtest.c b/accel/qtest/qtest.c
similarity index 86%
rename from accel/qtest.c
rename to accel/qtest/qtest.c
index 119d0f16a4..537e8b449c 100644
--- a/accel/qtest.c
+++ b/accel/qtest/qtest.c
@@ -12,6 +12,7 @@ 
  */
 
 #include "qemu/osdep.h"
+#include "qemu/rcu.h"
 #include "qapi/error.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
@@ -20,9 +21,15 @@ 
 #include "sysemu/qtest.h"
 #include "sysemu/cpus.h"
 #include "sysemu/cpu-timers.h"
+#include "qemu/guest-random.h"
+#include "qemu/main-loop.h"
+#include "hw/core/cpu.h"
+
+#include "qtest-cpus.h"
 
 static int qtest_init_accel(MachineState *ms)
 {
+    cpus_register_accel(&qtest_cpus);
     return 0;
 }
 
diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c
index 82f118d2df..69f8a842da 100644
--- a/accel/stubs/kvm-stub.c
+++ b/accel/stubs/kvm-stub.c
@@ -32,9 +32,8 @@  bool kvm_readonly_mem_allowed;
 bool kvm_ioeventfd_any_length_allowed;
 bool kvm_msi_use_devid;
 
-int kvm_destroy_vcpu(CPUState *cpu)
+void kvm_destroy_vcpu(CPUState *cpu)
 {
-    return -ENOSYS;
 }
 
 int kvm_init_vcpu(CPUState *cpu)
diff --git a/accel/tcg/Makefile.objs b/accel/tcg/Makefile.objs
index a92f2c454b..ecf9aa582e 100644
--- a/accel/tcg/Makefile.objs
+++ b/accel/tcg/Makefile.objs
@@ -1,5 +1,6 @@ 
 obj-$(CONFIG_SOFTMMU) += tcg-all.o
 obj-$(CONFIG_SOFTMMU) += cputlb.o
+obj-$(CONFIG_SOFTMMU) += tcg-cpus.o
 obj-y += tcg-runtime.o tcg-runtime-gvec.o
 obj-y += cpu-exec.o cpu-exec-common.o translate-all.o
 obj-y += translator.o
diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index e27385d051..3fd4bf2cab 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -24,19 +24,17 @@ 
  */
 
 #include "qemu/osdep.h"
-#include "sysemu/accel.h"
+#include "qemu-common.h"
 #include "sysemu/tcg.h"
-#include "qom/object.h"
-#include "cpu.h"
-#include "sysemu/cpus.h"
 #include "sysemu/cpu-timers.h"
-#include "qemu/main-loop.h"
 #include "tcg/tcg.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "hw/boards.h"
 #include "qapi/qapi-builtin-visit.h"
 
+#include "tcg-cpus.h"
+
 typedef struct TCGState {
     AccelState parent_obj;
 
@@ -123,6 +121,8 @@  static void tcg_accel_instance_init(Object *obj)
     s->mttcg_enabled = default_mttcg_enabled();
 }
 
+bool mttcg_enabled;
+
 static int tcg_init(MachineState *ms)
 {
     TCGState *s = TCG_STATE(current_accel());
@@ -130,6 +130,8 @@  static int tcg_init(MachineState *ms)
     tcg_exec_init(s->tb_size * 1024 * 1024);
     cpu_interrupt_handler = tcg_handle_interrupt;
     mttcg_enabled = s->mttcg_enabled;
+    cpus_register_accel(&tcg_cpus);
+
     return 0;
 }
 
diff --git a/accel/tcg/tcg-cpus.c b/accel/tcg/tcg-cpus.c
new file mode 100644
index 0000000000..9bede84d3e
--- /dev/null
+++ b/accel/tcg/tcg-cpus.c
@@ -0,0 +1,523 @@ 
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ * Copyright (c) 2014 Red Hat Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/tcg.h"
+#include "sysemu/replay.h"
+#include "qemu/main-loop.h"
+#include "qemu/guest-random.h"
+#include "exec/exec-all.h"
+
+#include "tcg-cpus.h"
+
+/* Kick all RR vCPUs */
+static void qemu_cpu_kick_rr_cpus(void)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        cpu_exit(cpu);
+    };
+}
+
+static void tcg_kick_vcpu_thread(CPUState *cpu)
+{
+    if (qemu_tcg_mttcg_enabled()) {
+        cpu_exit(cpu);
+    } else {
+        qemu_cpu_kick_rr_cpus();
+    }
+}
+
+/*
+ * TCG vCPU kick timer
+ *
+ * The kick timer is responsible for moving single threaded vCPU
+ * emulation on to the next vCPU. If more than one vCPU is running a
+ * timer event with force a cpu->exit so the next vCPU can get
+ * scheduled.
+ *
+ * The timer is removed if all vCPUs are idle and restarted again once
+ * idleness is complete.
+ */
+
+static QEMUTimer *tcg_kick_vcpu_timer;
+static CPUState *tcg_current_rr_cpu;
+
+#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
+
+static inline int64_t qemu_tcg_next_kick(void)
+{
+    return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
+}
+
+/* Kick the currently round-robin scheduled vCPU to next */
+static void qemu_cpu_kick_rr_next_cpu(void)
+{
+    CPUState *cpu;
+    do {
+        cpu = atomic_mb_read(&tcg_current_rr_cpu);
+        if (cpu) {
+            cpu_exit(cpu);
+        }
+    } while (cpu != atomic_mb_read(&tcg_current_rr_cpu));
+}
+
+static void kick_tcg_thread(void *opaque)
+{
+    timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
+    qemu_cpu_kick_rr_next_cpu();
+}
+
+static void start_tcg_kick_timer(void)
+{
+    assert(!mttcg_enabled);
+    if (!tcg_kick_vcpu_timer && CPU_NEXT(first_cpu)) {
+        tcg_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                                           kick_tcg_thread, NULL);
+    }
+    if (tcg_kick_vcpu_timer && !timer_pending(tcg_kick_vcpu_timer)) {
+        timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
+    }
+}
+
+static void stop_tcg_kick_timer(void)
+{
+    assert(!mttcg_enabled);
+    if (tcg_kick_vcpu_timer && timer_pending(tcg_kick_vcpu_timer)) {
+        timer_del(tcg_kick_vcpu_timer);
+    }
+}
+
+static void qemu_tcg_destroy_vcpu(CPUState *cpu)
+{
+}
+
+static void qemu_tcg_rr_wait_io_event(void)
+{
+    CPUState *cpu;
+
+    while (all_cpu_threads_idle()) {
+        stop_tcg_kick_timer();
+        qemu_cond_wait_iothread(first_cpu->halt_cond);
+    }
+
+    start_tcg_kick_timer();
+
+    CPU_FOREACH(cpu) {
+        qemu_wait_io_event_common(cpu);
+    }
+}
+
+static int64_t tcg_get_icount_limit(void)
+{
+    int64_t deadline;
+
+    if (replay_mode != REPLAY_MODE_PLAY) {
+        /*
+         * Include all the timers, because they may need an attention.
+         * Too long CPU execution may create unnecessary delay in UI.
+         */
+        deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
+                                              QEMU_TIMER_ATTR_ALL);
+        /* Check realtime timers, because they help with input processing */
+        deadline = qemu_soonest_timeout(deadline,
+                qemu_clock_deadline_ns_all(QEMU_CLOCK_REALTIME,
+                                           QEMU_TIMER_ATTR_ALL));
+
+        /*
+         * Maintain prior (possibly buggy) behaviour where if no deadline
+         * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
+         * INT32_MAX nanoseconds ahead, we still use INT32_MAX
+         * nanoseconds.
+         */
+        if ((deadline < 0) || (deadline > INT32_MAX)) {
+            deadline = INT32_MAX;
+        }
+
+        return icount_round(deadline);
+    } else {
+        return replay_get_instructions();
+    }
+}
+
+static void handle_icount_deadline(void)
+{
+    assert(qemu_in_vcpu_thread());
+    if (icount_enabled()) {
+        int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
+                                                      QEMU_TIMER_ATTR_ALL);
+
+        if (deadline == 0) {
+            /* Wake up other AioContexts.  */
+            qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
+            qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
+        }
+    }
+}
+
+static void prepare_icount_for_run(CPUState *cpu)
+{
+    if (icount_enabled()) {
+        int insns_left;
+
+        /*
+         * These should always be cleared by process_icount_data after
+         * each vCPU execution. However u16.high can be raised
+         * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt
+         */
+        g_assert(cpu_neg(cpu)->icount_decr.u16.low == 0);
+        g_assert(cpu->icount_extra == 0);
+
+        cpu->icount_budget = tcg_get_icount_limit();
+        insns_left = MIN(0xffff, cpu->icount_budget);
+        cpu_neg(cpu)->icount_decr.u16.low = insns_left;
+        cpu->icount_extra = cpu->icount_budget - insns_left;
+
+        replay_mutex_lock();
+    }
+}
+
+static void process_icount_data(CPUState *cpu)
+{
+    if (icount_enabled()) {
+        /* Account for executed instructions */
+        icount_update(cpu);
+
+        /* Reset the counters */
+        cpu_neg(cpu)->icount_decr.u16.low = 0;
+        cpu->icount_extra = 0;
+        cpu->icount_budget = 0;
+
+        replay_account_executed_instructions();
+
+        replay_mutex_unlock();
+    }
+}
+
+static int tcg_cpu_exec(CPUState *cpu)
+{
+    int ret;
+#ifdef CONFIG_PROFILER
+    int64_t ti;
+#endif
+
+    assert(tcg_enabled());
+#ifdef CONFIG_PROFILER
+    ti = profile_getclock();
+#endif
+    cpu_exec_start(cpu);
+    ret = cpu_exec(cpu);
+    cpu_exec_end(cpu);
+#ifdef CONFIG_PROFILER
+    atomic_set(&tcg_ctx->prof.cpu_exec_time,
+               tcg_ctx->prof.cpu_exec_time + profile_getclock() - ti);
+#endif
+    return ret;
+}
+
+/*
+ * Destroy any remaining vCPUs which have been unplugged and have
+ * finished running
+ */
+static void deal_with_unplugged_cpus(void)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        if (cpu->unplug && !cpu_can_run(cpu)) {
+            qemu_tcg_destroy_vcpu(cpu);
+            cpu_thread_signal_destroyed(cpu);
+            break;
+        }
+    }
+}
+
+/*
+ * Single-threaded TCG
+ *
+ * In the single-threaded case each vCPU is simulated in turn. If
+ * there is more than a single vCPU we create a simple timer to kick
+ * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
+ * This is done explicitly rather than relying on side-effects
+ * elsewhere.
+ */
+
+static void *tcg_rr_cpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+
+    assert(tcg_enabled());
+    rcu_register_thread();
+    tcg_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+
+    cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    /* wait for initial kick-off after machine start */
+    while (first_cpu->stopped) {
+        qemu_cond_wait_iothread(first_cpu->halt_cond);
+
+        /* process any pending work */
+        CPU_FOREACH(cpu) {
+            current_cpu = cpu;
+            qemu_wait_io_event_common(cpu);
+        }
+    }
+
+    start_tcg_kick_timer();
+
+    cpu = first_cpu;
+
+    /* process any pending work */
+    cpu->exit_request = 1;
+
+    while (1) {
+        qemu_mutex_unlock_iothread();
+        replay_mutex_lock();
+        qemu_mutex_lock_iothread();
+        /* Account partial waits to QEMU_CLOCK_VIRTUAL.  */
+        icount_account_warp_timer();
+
+        /*
+         * Run the timers here.  This is much more efficient than
+         * waking up the I/O thread and waiting for completion.
+         */
+        handle_icount_deadline();
+
+        replay_mutex_unlock();
+
+        if (!cpu) {
+            cpu = first_cpu;
+        }
+
+        while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
+
+            atomic_mb_set(&tcg_current_rr_cpu, cpu);
+            current_cpu = cpu;
+
+            qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
+                              (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
+
+            if (cpu_can_run(cpu)) {
+                int r;
+
+                qemu_mutex_unlock_iothread();
+                prepare_icount_for_run(cpu);
+
+                r = tcg_cpu_exec(cpu);
+
+                process_icount_data(cpu);
+                qemu_mutex_lock_iothread();
+
+                if (r == EXCP_DEBUG) {
+                    cpu_handle_guest_debug(cpu);
+                    break;
+                } else if (r == EXCP_ATOMIC) {
+                    qemu_mutex_unlock_iothread();
+                    cpu_exec_step_atomic(cpu);
+                    qemu_mutex_lock_iothread();
+                    break;
+                }
+            } else if (cpu->stop) {
+                if (cpu->unplug) {
+                    cpu = CPU_NEXT(cpu);
+                }
+                break;
+            }
+
+            cpu = CPU_NEXT(cpu);
+        } /* while (cpu && !cpu->exit_request).. */
+
+        /* Does not need atomic_mb_set because a spurious wakeup is okay.  */
+        atomic_set(&tcg_current_rr_cpu, NULL);
+
+        if (cpu && cpu->exit_request) {
+            atomic_mb_set(&cpu->exit_request, 0);
+        }
+
+        if (icount_enabled() && all_cpu_threads_idle()) {
+            /*
+             * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
+             * in the main_loop, wake it up in order to start the warp timer.
+             */
+            qemu_notify_event();
+        }
+
+        qemu_tcg_rr_wait_io_event();
+        deal_with_unplugged_cpus();
+    }
+
+    rcu_unregister_thread();
+    return NULL;
+}
+
+/*
+ * Multi-threaded TCG
+ *
+ * In the multi-threaded case each vCPU has its own thread. The TLS
+ * variable current_cpu can be used deep in the code to find the
+ * current CPUState for a given thread.
+ */
+
+static void *tcg_cpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+
+    assert(tcg_enabled());
+    g_assert(!icount_enabled());
+
+    rcu_register_thread();
+    tcg_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+
+    cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
+    current_cpu = cpu;
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    /* process any pending work */
+    cpu->exit_request = 1;
+
+    do {
+        if (cpu_can_run(cpu)) {
+            int r;
+            qemu_mutex_unlock_iothread();
+            r = tcg_cpu_exec(cpu);
+            qemu_mutex_lock_iothread();
+            switch (r) {
+            case EXCP_DEBUG:
+                cpu_handle_guest_debug(cpu);
+                break;
+            case EXCP_HALTED:
+                /*
+                 * during start-up the vCPU is reset and the thread is
+                 * kicked several times. If we don't ensure we go back
+                 * to sleep in the halted state we won't cleanly
+                 * start-up when the vCPU is enabled.
+                 *
+                 * cpu->halted should ensure we sleep in wait_io_event
+                 */
+                g_assert(cpu->halted);
+                break;
+            case EXCP_ATOMIC:
+                qemu_mutex_unlock_iothread();
+                cpu_exec_step_atomic(cpu);
+                qemu_mutex_lock_iothread();
+            default:
+                /* Ignore everything else? */
+                break;
+            }
+        }
+
+        atomic_mb_set(&cpu->exit_request, 0);
+        qemu_wait_io_event(cpu);
+    } while (!cpu->unplug || cpu_can_run(cpu));
+
+    qemu_tcg_destroy_vcpu(cpu);
+    cpu_thread_signal_destroyed(cpu);
+    qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static void tcg_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+    static QemuCond *single_tcg_halt_cond;
+    static QemuThread *single_tcg_cpu_thread;
+    static int tcg_region_inited;
+
+    assert(tcg_enabled());
+    /*
+     * Initialize TCG regions--once. Now is a good time, because:
+     * (1) TCG's init context, prologue and target globals have been set up.
+     * (2) qemu_tcg_mttcg_enabled() works now (TCG init code runs before the
+     *     -accel flag is processed, so the check doesn't work then).
+     */
+    if (!tcg_region_inited) {
+        tcg_region_inited = 1;
+        tcg_region_init();
+    }
+
+    if (qemu_tcg_mttcg_enabled() || !single_tcg_cpu_thread) {
+        cpu->thread = g_malloc0(sizeof(QemuThread));
+        cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+        qemu_cond_init(cpu->halt_cond);
+
+        if (qemu_tcg_mttcg_enabled()) {
+            /* create a thread per vCPU with TCG (MTTCG) */
+            parallel_cpus = true;
+            snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
+                 cpu->cpu_index);
+
+            qemu_thread_create(cpu->thread, thread_name, tcg_cpu_thread_fn,
+                               cpu, QEMU_THREAD_JOINABLE);
+
+        } else {
+            /* share a single thread for all cpus with TCG */
+            snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG");
+            qemu_thread_create(cpu->thread, thread_name,
+                               tcg_rr_cpu_thread_fn,
+                               cpu, QEMU_THREAD_JOINABLE);
+
+            single_tcg_halt_cond = cpu->halt_cond;
+            single_tcg_cpu_thread = cpu->thread;
+        }
+#ifdef _WIN32
+        cpu->hThread = qemu_thread_get_handle(cpu->thread);
+#endif
+    } else {
+        /* For non-MTTCG cases we share the thread */
+        cpu->thread = single_tcg_cpu_thread;
+        cpu->halt_cond = single_tcg_halt_cond;
+        cpu->thread_id = first_cpu->thread_id;
+        cpu->can_do_io = 1;
+        cpu->created = true;
+    }
+}
+
+static void tcg_cpu_synchronize_noop(CPUState *cpu)
+{
+}
+
+CpusAccel tcg_cpus = {
+    .create_vcpu_thread = tcg_start_vcpu_thread,
+    .kick_vcpu_thread = tcg_kick_vcpu_thread,
+
+    .synchronize_post_reset = tcg_cpu_synchronize_noop,
+    .synchronize_post_init = tcg_cpu_synchronize_noop,
+    .synchronize_state = tcg_cpu_synchronize_noop,
+    .synchronize_pre_loadvm = tcg_cpu_synchronize_noop,
+};
diff --git a/accel/tcg/tcg-cpus.h b/accel/tcg/tcg-cpus.h
new file mode 100644
index 0000000000..af4be6a151
--- /dev/null
+++ b/accel/tcg/tcg-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef TCG_CPUS_H
+#define TCG_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel tcg_cpus;
+
+#endif /* TCG_CPUS_H */
diff --git a/hw/core/cpu.c b/hw/core/cpu.c
index f31ec48ee6..379aa2fe99 100644
--- a/hw/core/cpu.c
+++ b/hw/core/cpu.c
@@ -33,6 +33,7 @@ 
 #include "hw/qdev-properties.h"
 #include "trace-root.h"
 #include "qemu/plugin.h"
+#include "sysemu/hw_accel.h"
 
 CPUInterruptHandler cpu_interrupt_handler;
 
diff --git a/include/sysemu/cpus.h b/include/sysemu/cpus.h
index 149de000a0..62b6f43e14 100644
--- a/include/sysemu/cpus.h
+++ b/include/sysemu/cpus.h
@@ -4,7 +4,39 @@ 
 #include "qemu/timer.h"
 
 /* cpus.c */
+
+/* CPU execution threads */
+
+typedef struct CpusAccel {
+    void (*create_vcpu_thread)(CPUState *cpu);
+    void (*kick_vcpu_thread)(CPUState *cpu);
+
+    void (*synchronize_post_reset)(CPUState *cpu);
+    void (*synchronize_post_init)(CPUState *cpu);
+    void (*synchronize_state)(CPUState *cpu);
+    void (*synchronize_pre_loadvm)(CPUState *cpu);
+} CpusAccel;
+
+/* register accel-specific cpus interface implementation */
+void cpus_register_accel(CpusAccel *i);
+
+/* interface available for cpus accelerator threads */
+
+/* For temporary buffers for forming a name */
+#define VCPU_THREAD_NAME_SIZE 16
+
+void cpus_kick_thread(CPUState *cpu);
+bool cpu_thread_is_idle(CPUState *cpu);
 bool all_cpu_threads_idle(void);
+bool cpu_can_run(CPUState *cpu);
+void qemu_wait_io_event_common(CPUState *cpu);
+void qemu_wait_io_event(CPUState *cpu);
+void cpu_thread_signal_created(CPUState *cpu);
+void cpu_thread_signal_destroyed(CPUState *cpu);
+void cpu_handle_guest_debug(CPUState *cpu);
+
+/* end interface for cpus accelerator threads */
+
 bool qemu_in_vcpu_thread(void);
 void qemu_init_cpu_loop(void);
 void resume_all_vcpus(void);
diff --git a/include/sysemu/hw_accel.h b/include/sysemu/hw_accel.h
index 0ec2372477..336740e10a 100644
--- a/include/sysemu/hw_accel.h
+++ b/include/sysemu/hw_accel.h
@@ -1,5 +1,5 @@ 
 /*
- * QEMU Hardware accelertors support
+ * QEMU Hardware accelerators support
  *
  * Copyright 2016 Google, Inc.
  *
@@ -16,56 +16,9 @@ 
 #include "sysemu/kvm.h"
 #include "sysemu/whpx.h"
 
-static inline void cpu_synchronize_state(CPUState *cpu)
-{
-    if (kvm_enabled()) {
-        kvm_cpu_synchronize_state(cpu);
-    }
-    if (hax_enabled()) {
-        hax_cpu_synchronize_state(cpu);
-    }
-    if (whpx_enabled()) {
-        whpx_cpu_synchronize_state(cpu);
-    }
-}
-
-static inline void cpu_synchronize_post_reset(CPUState *cpu)
-{
-    if (kvm_enabled()) {
-        kvm_cpu_synchronize_post_reset(cpu);
-    }
-    if (hax_enabled()) {
-        hax_cpu_synchronize_post_reset(cpu);
-    }
-    if (whpx_enabled()) {
-        whpx_cpu_synchronize_post_reset(cpu);
-    }
-}
-
-static inline void cpu_synchronize_post_init(CPUState *cpu)
-{
-    if (kvm_enabled()) {
-        kvm_cpu_synchronize_post_init(cpu);
-    }
-    if (hax_enabled()) {
-        hax_cpu_synchronize_post_init(cpu);
-    }
-    if (whpx_enabled()) {
-        whpx_cpu_synchronize_post_init(cpu);
-    }
-}
-
-static inline void cpu_synchronize_pre_loadvm(CPUState *cpu)
-{
-    if (kvm_enabled()) {
-        kvm_cpu_synchronize_pre_loadvm(cpu);
-    }
-    if (hax_enabled()) {
-        hax_cpu_synchronize_pre_loadvm(cpu);
-    }
-    if (whpx_enabled()) {
-        whpx_cpu_synchronize_pre_loadvm(cpu);
-    }
-}
+void cpu_synchronize_state(CPUState *cpu);
+void cpu_synchronize_post_reset(CPUState *cpu);
+void cpu_synchronize_post_init(CPUState *cpu);
+void cpu_synchronize_pre_loadvm(CPUState *cpu);
 
 #endif /* QEMU_HW_ACCEL_H */
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index b4174d941c..7a5f973b6f 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -218,7 +218,7 @@  int kvm_has_intx_set_mask(void);
 
 int kvm_init_vcpu(CPUState *cpu);
 int kvm_cpu_exec(CPUState *cpu);
-int kvm_destroy_vcpu(CPUState *cpu);
+void kvm_destroy_vcpu(CPUState *cpu);
 
 /**
  * kvm_arm_supports_user_irq
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index c355263e89..835708ce03 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -24,27 +24,19 @@ 
 
 #include "qemu/osdep.h"
 #include "qemu-common.h"
-#include "qemu/config-file.h"
-#include "qemu/cutils.h"
-#include "migration/vmstate.h"
 #include "monitor/monitor.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-misc.h"
 #include "qapi/qapi-events-run-state.h"
 #include "qapi/qmp/qerror.h"
-#include "qemu/error-report.h"
-#include "qemu/qemu-print.h"
 #include "sysemu/tcg.h"
-#include "sysemu/block-backend.h"
 #include "exec/gdbstub.h"
-#include "sysemu/dma.h"
 #include "sysemu/hw_accel.h"
 #include "sysemu/kvm.h"
 #include "sysemu/hax.h"
 #include "sysemu/hvf.h"
 #include "sysemu/whpx.h"
 #include "exec/exec-all.h"
-
 #include "qemu/thread.h"
 #include "qemu/plugin.h"
 #include "sysemu/cpus.h"
@@ -87,7 +79,7 @@  bool cpu_is_stopped(CPUState *cpu)
     return cpu->stopped || !runstate_is_running();
 }
 
-static bool cpu_thread_is_idle(CPUState *cpu)
+bool cpu_thread_is_idle(CPUState *cpu)
 {
     if (cpu->stop || cpu->queued_work_first) {
         return false;
@@ -114,79 +106,6 @@  bool all_cpu_threads_idle(void)
     return true;
 }
 
-bool mttcg_enabled;
-
-
-/***********************************************************/
-/* TCG vCPU kick timer
- *
- * The kick timer is responsible for moving single threaded vCPU
- * emulation on to the next vCPU. If more than one vCPU is running a
- * timer event with force a cpu->exit so the next vCPU can get
- * scheduled.
- *
- * The timer is removed if all vCPUs are idle and restarted again once
- * idleness is complete.
- */
-
-static QEMUTimer *tcg_kick_vcpu_timer;
-static CPUState *tcg_current_rr_cpu;
-
-#define TCG_KICK_PERIOD (NANOSECONDS_PER_SECOND / 10)
-
-static inline int64_t qemu_tcg_next_kick(void)
-{
-    return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + TCG_KICK_PERIOD;
-}
-
-/* Kick the currently round-robin scheduled vCPU to next */
-static void qemu_cpu_kick_rr_next_cpu(void)
-{
-    CPUState *cpu;
-    do {
-        cpu = atomic_mb_read(&tcg_current_rr_cpu);
-        if (cpu) {
-            cpu_exit(cpu);
-        }
-    } while (cpu != atomic_mb_read(&tcg_current_rr_cpu));
-}
-
-/* Kick all RR vCPUs */
-static void qemu_cpu_kick_rr_cpus(void)
-{
-    CPUState *cpu;
-
-    CPU_FOREACH(cpu) {
-        cpu_exit(cpu);
-    };
-}
-
-static void kick_tcg_thread(void *opaque)
-{
-    timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
-    qemu_cpu_kick_rr_next_cpu();
-}
-
-static void start_tcg_kick_timer(void)
-{
-    assert(!mttcg_enabled);
-    if (!tcg_kick_vcpu_timer && CPU_NEXT(first_cpu)) {
-        tcg_kick_vcpu_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
-                                           kick_tcg_thread, NULL);
-    }
-    if (tcg_kick_vcpu_timer && !timer_pending(tcg_kick_vcpu_timer)) {
-        timer_mod(tcg_kick_vcpu_timer, qemu_tcg_next_kick());
-    }
-}
-
-static void stop_tcg_kick_timer(void)
-{
-    assert(!mttcg_enabled);
-    if (tcg_kick_vcpu_timer && timer_pending(tcg_kick_vcpu_timer)) {
-        timer_del(tcg_kick_vcpu_timer);
-    }
-}
-
 /***********************************************************/
 void hw_error(const char *fmt, ...)
 {
@@ -205,16 +124,20 @@  void hw_error(const char *fmt, ...)
     abort();
 }
 
+/*
+ * every accelerator is supposed to register this.
+ * Could be in the AccelClass instead, but ends up being too complicated
+ * to access in practice, and inefficient for each call of each method.
+ */
+static CpusAccel cpus_accel;
+
 void cpu_synchronize_all_states(void)
 {
     CPUState *cpu;
 
     CPU_FOREACH(cpu) {
-        cpu_synchronize_state(cpu);
-        /* TODO: move to cpu_synchronize_state() */
-        if (hvf_enabled()) {
-            hvf_cpu_synchronize_state(cpu);
-        }
+        assert(cpus_accel.synchronize_state != NULL);
+        cpus_accel.synchronize_state(cpu);
     }
 }
 
@@ -223,11 +146,8 @@  void cpu_synchronize_all_post_reset(void)
     CPUState *cpu;
 
     CPU_FOREACH(cpu) {
-        cpu_synchronize_post_reset(cpu);
-        /* TODO: move to cpu_synchronize_post_reset() */
-        if (hvf_enabled()) {
-            hvf_cpu_synchronize_post_reset(cpu);
-        }
+        assert(cpus_accel.synchronize_post_reset != NULL);
+        cpus_accel.synchronize_post_reset(cpu);
     }
 }
 
@@ -236,11 +156,8 @@  void cpu_synchronize_all_post_init(void)
     CPUState *cpu;
 
     CPU_FOREACH(cpu) {
-        cpu_synchronize_post_init(cpu);
-        /* TODO: move to cpu_synchronize_post_init() */
-        if (hvf_enabled()) {
-            hvf_cpu_synchronize_post_init(cpu);
-        }
+        assert(cpus_accel.synchronize_post_init != NULL);
+        cpus_accel.synchronize_post_init(cpu);
     }
 }
 
@@ -249,7 +166,8 @@  void cpu_synchronize_all_pre_loadvm(void)
     CPUState *cpu;
 
     CPU_FOREACH(cpu) {
-        cpu_synchronize_pre_loadvm(cpu);
+        assert(cpus_accel.synchronize_pre_loadvm != NULL);
+        cpus_accel.synchronize_pre_loadvm(cpu);
     }
 }
 
@@ -281,7 +199,7 @@  int vm_shutdown(void)
     return do_vm_stop(RUN_STATE_SHUTDOWN, false);
 }
 
-static bool cpu_can_run(CPUState *cpu)
+bool cpu_can_run(CPUState *cpu)
 {
     if (cpu->stop) {
         return false;
@@ -292,7 +210,7 @@  static bool cpu_can_run(CPUState *cpu)
     return true;
 }
 
-static void cpu_handle_guest_debug(CPUState *cpu)
+void cpu_handle_guest_debug(CPUState *cpu)
 {
     gdb_set_stop_cpu(cpu);
     qemu_system_debug_request();
@@ -375,18 +293,6 @@  void run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data)
     do_run_on_cpu(cpu, func, data, &qemu_global_mutex);
 }
 
-static void qemu_kvm_destroy_vcpu(CPUState *cpu)
-{
-    if (kvm_destroy_vcpu(cpu) < 0) {
-        error_report("kvm_destroy_vcpu failed");
-        exit(EXIT_FAILURE);
-    }
-}
-
-static void qemu_tcg_destroy_vcpu(CPUState *cpu)
-{
-}
-
 static void qemu_cpu_stop(CPUState *cpu, bool exit)
 {
     g_assert(qemu_cpu_is_self(cpu));
@@ -398,7 +304,7 @@  static void qemu_cpu_stop(CPUState *cpu, bool exit)
     qemu_cond_broadcast(&qemu_pause_cond);
 }
 
-static void qemu_wait_io_event_common(CPUState *cpu)
+void qemu_wait_io_event_common(CPUState *cpu)
 {
     atomic_mb_set(&cpu->thread_kicked, false);
     if (cpu->stop) {
@@ -407,23 +313,7 @@  static void qemu_wait_io_event_common(CPUState *cpu)
     process_queued_cpu_work(cpu);
 }
 
-static void qemu_tcg_rr_wait_io_event(void)
-{
-    CPUState *cpu;
-
-    while (all_cpu_threads_idle()) {
-        stop_tcg_kick_timer();
-        qemu_cond_wait(first_cpu->halt_cond, &qemu_global_mutex);
-    }
-
-    start_tcg_kick_timer();
-
-    CPU_FOREACH(cpu) {
-        qemu_wait_io_event_common(cpu);
-    }
-}
-
-static void qemu_wait_io_event(CPUState *cpu)
+void qemu_wait_io_event(CPUState *cpu)
 {
     bool slept = false;
 
@@ -439,7 +329,8 @@  static void qemu_wait_io_event(CPUState *cpu)
     }
 
 #ifdef _WIN32
-    /* Eat dummy APC queued by qemu_cpu_kick_thread.  */
+    /* Eat dummy APC queued by hax_kick_vcpu_thread */
+    /* NB!!! Should not this be if (hax_enabled)? Is this wrong for whpx? */
     if (!tcg_enabled()) {
         SleepEx(0, TRUE);
     }
@@ -447,540 +338,7 @@  static void qemu_wait_io_event(CPUState *cpu)
     qemu_wait_io_event_common(cpu);
 }
 
-static void *qemu_kvm_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-    int r;
-
-    rcu_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->can_do_io = 1;
-    current_cpu = cpu;
-
-    r = kvm_init_vcpu(cpu);
-    if (r < 0) {
-        error_report("kvm_init_vcpu failed: %s", strerror(-r));
-        exit(1);
-    }
-
-    kvm_init_cpu_signals(cpu);
-
-    /* signal CPU creation */
-    cpu->created = true;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    do {
-        if (cpu_can_run(cpu)) {
-            r = kvm_cpu_exec(cpu);
-            if (r == EXCP_DEBUG) {
-                cpu_handle_guest_debug(cpu);
-            }
-        }
-        qemu_wait_io_event(cpu);
-    } while (!cpu->unplug || cpu_can_run(cpu));
-
-    qemu_kvm_destroy_vcpu(cpu);
-    cpu->created = false;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_mutex_unlock_iothread();
-    rcu_unregister_thread();
-    return NULL;
-}
-
-static void *qemu_dummy_cpu_thread_fn(void *arg)
-{
-#ifdef _WIN32
-    error_report("qtest is not supported under Windows");
-    exit(1);
-#else
-    CPUState *cpu = arg;
-    sigset_t waitset;
-    int r;
-
-    rcu_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->can_do_io = 1;
-    current_cpu = cpu;
-
-    sigemptyset(&waitset);
-    sigaddset(&waitset, SIG_IPI);
-
-    /* signal CPU creation */
-    cpu->created = true;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    do {
-        qemu_mutex_unlock_iothread();
-        do {
-            int sig;
-            r = sigwait(&waitset, &sig);
-        } while (r == -1 && (errno == EAGAIN || errno == EINTR));
-        if (r == -1) {
-            perror("sigwait");
-            exit(1);
-        }
-        qemu_mutex_lock_iothread();
-        qemu_wait_io_event(cpu);
-    } while (!cpu->unplug);
-
-    qemu_mutex_unlock_iothread();
-    rcu_unregister_thread();
-    return NULL;
-#endif
-}
-
-static int64_t tcg_get_icount_limit(void)
-{
-    int64_t deadline;
-
-    if (replay_mode != REPLAY_MODE_PLAY) {
-        /*
-         * Include all the timers, because they may need an attention.
-         * Too long CPU execution may create unnecessary delay in UI.
-         */
-        deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
-                                              QEMU_TIMER_ATTR_ALL);
-        /* Check realtime timers, because they help with input processing */
-        deadline = qemu_soonest_timeout(deadline,
-                qemu_clock_deadline_ns_all(QEMU_CLOCK_REALTIME,
-                                           QEMU_TIMER_ATTR_ALL));
-
-        /* Maintain prior (possibly buggy) behaviour where if no deadline
-         * was set (as there is no QEMU_CLOCK_VIRTUAL timer) or it is more than
-         * INT32_MAX nanoseconds ahead, we still use INT32_MAX
-         * nanoseconds.
-         */
-        if ((deadline < 0) || (deadline > INT32_MAX)) {
-            deadline = INT32_MAX;
-        }
-
-        return icount_round(deadline);
-    } else {
-        return replay_get_instructions();
-    }
-}
-
-static void handle_icount_deadline(void)
-{
-    assert(qemu_in_vcpu_thread());
-    if (icount_enabled()) {
-        int64_t deadline = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
-                                                      QEMU_TIMER_ATTR_ALL);
-
-        if (deadline == 0) {
-            /* Wake up other AioContexts.  */
-            qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
-            qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
-        }
-    }
-}
-
-static void prepare_icount_for_run(CPUState *cpu)
-{
-    if (icount_enabled()) {
-        int insns_left;
-
-        /* These should always be cleared by process_icount_data after
-         * each vCPU execution. However u16.high can be raised
-         * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt
-         */
-        g_assert(cpu_neg(cpu)->icount_decr.u16.low == 0);
-        g_assert(cpu->icount_extra == 0);
-
-        cpu->icount_budget = tcg_get_icount_limit();
-        insns_left = MIN(0xffff, cpu->icount_budget);
-        cpu_neg(cpu)->icount_decr.u16.low = insns_left;
-        cpu->icount_extra = cpu->icount_budget - insns_left;
-
-        replay_mutex_lock();
-    }
-}
-
-static void process_icount_data(CPUState *cpu)
-{
-    if (icount_enabled()) {
-        /* Account for executed instructions */
-        icount_update(cpu);
-
-        /* Reset the counters */
-        cpu_neg(cpu)->icount_decr.u16.low = 0;
-        cpu->icount_extra = 0;
-        cpu->icount_budget = 0;
-
-        replay_account_executed_instructions();
-
-        replay_mutex_unlock();
-    }
-}
-
-
-static int tcg_cpu_exec(CPUState *cpu)
-{
-    int ret;
-#ifdef CONFIG_PROFILER
-    int64_t ti;
-#endif
-
-    assert(tcg_enabled());
-#ifdef CONFIG_PROFILER
-    ti = profile_getclock();
-#endif
-    cpu_exec_start(cpu);
-    ret = cpu_exec(cpu);
-    cpu_exec_end(cpu);
-#ifdef CONFIG_PROFILER
-    atomic_set(&tcg_ctx->prof.cpu_exec_time,
-               tcg_ctx->prof.cpu_exec_time + profile_getclock() - ti);
-#endif
-    return ret;
-}
-
-/* Destroy any remaining vCPUs which have been unplugged and have
- * finished running
- */
-static void deal_with_unplugged_cpus(void)
-{
-    CPUState *cpu;
-
-    CPU_FOREACH(cpu) {
-        if (cpu->unplug && !cpu_can_run(cpu)) {
-            qemu_tcg_destroy_vcpu(cpu);
-            cpu->created = false;
-            qemu_cond_signal(&qemu_cpu_cond);
-            break;
-        }
-    }
-}
-
-/* Single-threaded TCG
- *
- * In the single-threaded case each vCPU is simulated in turn. If
- * there is more than a single vCPU we create a simple timer to kick
- * the vCPU and ensure we don't get stuck in a tight loop in one vCPU.
- * This is done explicitly rather than relying on side-effects
- * elsewhere.
- */
-
-static void *qemu_tcg_rr_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-
-    assert(tcg_enabled());
-    rcu_register_thread();
-    tcg_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->created = true;
-    cpu->can_do_io = 1;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    /* wait for initial kick-off after machine start */
-    while (first_cpu->stopped) {
-        qemu_cond_wait(first_cpu->halt_cond, &qemu_global_mutex);
-
-        /* process any pending work */
-        CPU_FOREACH(cpu) {
-            current_cpu = cpu;
-            qemu_wait_io_event_common(cpu);
-        }
-    }
-
-    start_tcg_kick_timer();
-
-    cpu = first_cpu;
-
-    /* process any pending work */
-    cpu->exit_request = 1;
-
-    while (1) {
-        qemu_mutex_unlock_iothread();
-        replay_mutex_lock();
-        qemu_mutex_lock_iothread();
-        /* Account partial waits to QEMU_CLOCK_VIRTUAL.  */
-        icount_account_warp_timer();
-
-        /* Run the timers here.  This is much more efficient than
-         * waking up the I/O thread and waiting for completion.
-         */
-        handle_icount_deadline();
-
-        replay_mutex_unlock();
-
-        if (!cpu) {
-            cpu = first_cpu;
-        }
-
-        while (cpu && !cpu->queued_work_first && !cpu->exit_request) {
-
-            atomic_mb_set(&tcg_current_rr_cpu, cpu);
-            current_cpu = cpu;
-
-            qemu_clock_enable(QEMU_CLOCK_VIRTUAL,
-                              (cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
-
-            if (cpu_can_run(cpu)) {
-                int r;
-
-                qemu_mutex_unlock_iothread();
-                prepare_icount_for_run(cpu);
-
-                r = tcg_cpu_exec(cpu);
-
-                process_icount_data(cpu);
-                qemu_mutex_lock_iothread();
-
-                if (r == EXCP_DEBUG) {
-                    cpu_handle_guest_debug(cpu);
-                    break;
-                } else if (r == EXCP_ATOMIC) {
-                    qemu_mutex_unlock_iothread();
-                    cpu_exec_step_atomic(cpu);
-                    qemu_mutex_lock_iothread();
-                    break;
-                }
-            } else if (cpu->stop) {
-                if (cpu->unplug) {
-                    cpu = CPU_NEXT(cpu);
-                }
-                break;
-            }
-
-            cpu = CPU_NEXT(cpu);
-        } /* while (cpu && !cpu->exit_request).. */
-
-        /* Does not need atomic_mb_set because a spurious wakeup is okay.  */
-        atomic_set(&tcg_current_rr_cpu, NULL);
-
-        if (cpu && cpu->exit_request) {
-            atomic_mb_set(&cpu->exit_request, 0);
-        }
-
-        if (icount_enabled() && all_cpu_threads_idle()) {
-            /*
-             * When all cpus are sleeping (e.g in WFI), to avoid a deadlock
-             * in the main_loop, wake it up in order to start the warp timer.
-             */
-            qemu_notify_event();
-        }
-
-        qemu_tcg_rr_wait_io_event();
-        deal_with_unplugged_cpus();
-    }
-
-    rcu_unregister_thread();
-    return NULL;
-}
-
-static void *qemu_hax_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-    int r;
-
-    rcu_register_thread();
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->created = true;
-    current_cpu = cpu;
-
-    hax_init_vcpu(cpu);
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    do {
-        if (cpu_can_run(cpu)) {
-            r = hax_smp_cpu_exec(cpu);
-            if (r == EXCP_DEBUG) {
-                cpu_handle_guest_debug(cpu);
-            }
-        }
-
-        qemu_wait_io_event(cpu);
-    } while (!cpu->unplug || cpu_can_run(cpu));
-    rcu_unregister_thread();
-    return NULL;
-}
-
-/* The HVF-specific vCPU thread function. This one should only run when the host
- * CPU supports the VMX "unrestricted guest" feature. */
-static void *qemu_hvf_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-
-    int r;
-
-    assert(hvf_enabled());
-
-    rcu_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->can_do_io = 1;
-    current_cpu = cpu;
-
-    hvf_init_vcpu(cpu);
-
-    /* signal CPU creation */
-    cpu->created = true;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    do {
-        if (cpu_can_run(cpu)) {
-            r = hvf_vcpu_exec(cpu);
-            if (r == EXCP_DEBUG) {
-                cpu_handle_guest_debug(cpu);
-            }
-        }
-        qemu_wait_io_event(cpu);
-    } while (!cpu->unplug || cpu_can_run(cpu));
-
-    hvf_vcpu_destroy(cpu);
-    cpu->created = false;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_mutex_unlock_iothread();
-    rcu_unregister_thread();
-    return NULL;
-}
-
-static void *qemu_whpx_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-    int r;
-
-    rcu_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-    cpu->thread_id = qemu_get_thread_id();
-    current_cpu = cpu;
-
-    r = whpx_init_vcpu(cpu);
-    if (r < 0) {
-        fprintf(stderr, "whpx_init_vcpu failed: %s\n", strerror(-r));
-        exit(1);
-    }
-
-    /* signal CPU creation */
-    cpu->created = true;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    do {
-        if (cpu_can_run(cpu)) {
-            r = whpx_vcpu_exec(cpu);
-            if (r == EXCP_DEBUG) {
-                cpu_handle_guest_debug(cpu);
-            }
-        }
-        while (cpu_thread_is_idle(cpu)) {
-            qemu_cond_wait(cpu->halt_cond, &qemu_global_mutex);
-        }
-        qemu_wait_io_event_common(cpu);
-    } while (!cpu->unplug || cpu_can_run(cpu));
-
-    whpx_destroy_vcpu(cpu);
-    cpu->created = false;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_mutex_unlock_iothread();
-    rcu_unregister_thread();
-    return NULL;
-}
-
-#ifdef _WIN32
-static void CALLBACK dummy_apc_func(ULONG_PTR unused)
-{
-}
-#endif
-
-/* Multi-threaded TCG
- *
- * In the multi-threaded case each vCPU has its own thread. The TLS
- * variable current_cpu can be used deep in the code to find the
- * current CPUState for a given thread.
- */
-
-static void *qemu_tcg_cpu_thread_fn(void *arg)
-{
-    CPUState *cpu = arg;
-
-    assert(tcg_enabled());
-    g_assert(!icount_enabled());
-
-    rcu_register_thread();
-    tcg_register_thread();
-
-    qemu_mutex_lock_iothread();
-    qemu_thread_get_self(cpu->thread);
-
-    cpu->thread_id = qemu_get_thread_id();
-    cpu->created = true;
-    cpu->can_do_io = 1;
-    current_cpu = cpu;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_guest_random_seed_thread_part2(cpu->random_seed);
-
-    /* process any pending work */
-    cpu->exit_request = 1;
-
-    do {
-        if (cpu_can_run(cpu)) {
-            int r;
-            qemu_mutex_unlock_iothread();
-            r = tcg_cpu_exec(cpu);
-            qemu_mutex_lock_iothread();
-            switch (r) {
-            case EXCP_DEBUG:
-                cpu_handle_guest_debug(cpu);
-                break;
-            case EXCP_HALTED:
-                /* during start-up the vCPU is reset and the thread is
-                 * kicked several times. If we don't ensure we go back
-                 * to sleep in the halted state we won't cleanly
-                 * start-up when the vCPU is enabled.
-                 *
-                 * cpu->halted should ensure we sleep in wait_io_event
-                 */
-                g_assert(cpu->halted);
-                break;
-            case EXCP_ATOMIC:
-                qemu_mutex_unlock_iothread();
-                cpu_exec_step_atomic(cpu);
-                qemu_mutex_lock_iothread();
-            default:
-                /* Ignore everything else? */
-                break;
-            }
-        }
-
-        atomic_mb_set(&cpu->exit_request, 0);
-        qemu_wait_io_event(cpu);
-    } while (!cpu->unplug || cpu_can_run(cpu));
-
-    qemu_tcg_destroy_vcpu(cpu);
-    cpu->created = false;
-    qemu_cond_signal(&qemu_cpu_cond);
-    qemu_mutex_unlock_iothread();
-    rcu_unregister_thread();
-    return NULL;
-}
-
-static void qemu_cpu_kick_thread(CPUState *cpu)
+void cpus_kick_thread(CPUState *cpu)
 {
 #ifndef _WIN32
     int err;
@@ -994,44 +352,20 @@  static void qemu_cpu_kick_thread(CPUState *cpu)
         fprintf(stderr, "qemu:%s: %s", __func__, strerror(err));
         exit(1);
     }
-#else /* _WIN32 */
-    if (!qemu_cpu_is_self(cpu)) {
-        if (whpx_enabled()) {
-            whpx_vcpu_kick(cpu);
-        } else if (!QueueUserAPC(dummy_apc_func, cpu->hThread, 0)) {
-            fprintf(stderr, "%s: QueueUserAPC failed with error %lu\n",
-                    __func__, GetLastError());
-            exit(1);
-        }
-    }
 #endif
 }
 
 void qemu_cpu_kick(CPUState *cpu)
 {
     qemu_cond_broadcast(cpu->halt_cond);
-    if (tcg_enabled()) {
-        if (qemu_tcg_mttcg_enabled()) {
-            cpu_exit(cpu);
-        } else {
-            qemu_cpu_kick_rr_cpus();
-        }
-    } else {
-        if (hax_enabled()) {
-            /*
-             * FIXME: race condition with the exit_request check in
-             * hax_vcpu_hax_exec
-             */
-            cpu->exit_request = 1;
-        }
-        qemu_cpu_kick_thread(cpu);
-    }
+    assert(cpus_accel.kick_vcpu_thread != NULL);
+    cpus_accel.kick_vcpu_thread(cpu);
 }
 
 void qemu_cpu_kick_self(void)
 {
     assert(current_cpu);
-    qemu_cpu_kick_thread(current_cpu);
+    cpus_kick_thread(current_cpu);
 }
 
 bool qemu_cpu_is_self(CPUState *cpu)
@@ -1081,6 +415,21 @@  void qemu_cond_timedwait_iothread(QemuCond *cond, int ms)
     qemu_cond_timedwait(cond, &qemu_global_mutex, ms);
 }
 
+/* signal CPU creation */
+void cpu_thread_signal_created(CPUState *cpu)
+{
+    cpu->created = true;
+    qemu_cond_signal(&qemu_cpu_cond);
+}
+
+/* signal CPU destruction */
+void cpu_thread_signal_destroyed(CPUState *cpu)
+{
+    cpu->created = false;
+    qemu_cond_signal(&qemu_cpu_cond);
+}
+
+
 static bool all_vcpus_paused(void)
 {
     CPUState *cpu;
@@ -1156,140 +505,18 @@  void cpu_remove_sync(CPUState *cpu)
     qemu_mutex_lock_iothread();
 }
 
-/* For temporary buffers for forming a name */
-#define VCPU_THREAD_NAME_SIZE 16
-
-static void qemu_tcg_init_vcpu(CPUState *cpu)
-{
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-    static QemuCond *single_tcg_halt_cond;
-    static QemuThread *single_tcg_cpu_thread;
-    static int tcg_region_inited;
-
-    assert(tcg_enabled());
-    /*
-     * Initialize TCG regions--once. Now is a good time, because:
-     * (1) TCG's init context, prologue and target globals have been set up.
-     * (2) qemu_tcg_mttcg_enabled() works now (TCG init code runs before the
-     *     -accel flag is processed, so the check doesn't work then).
-     */
-    if (!tcg_region_inited) {
-        tcg_region_inited = 1;
-        tcg_region_init();
-    }
-
-    if (qemu_tcg_mttcg_enabled() || !single_tcg_cpu_thread) {
-        cpu->thread = g_malloc0(sizeof(QemuThread));
-        cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-        qemu_cond_init(cpu->halt_cond);
-
-        if (qemu_tcg_mttcg_enabled()) {
-            /* create a thread per vCPU with TCG (MTTCG) */
-            parallel_cpus = true;
-            snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
-                 cpu->cpu_index);
-
-            qemu_thread_create(cpu->thread, thread_name, qemu_tcg_cpu_thread_fn,
-                               cpu, QEMU_THREAD_JOINABLE);
-
-        } else {
-            /* share a single thread for all cpus with TCG */
-            snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "ALL CPUs/TCG");
-            qemu_thread_create(cpu->thread, thread_name,
-                               qemu_tcg_rr_cpu_thread_fn,
-                               cpu, QEMU_THREAD_JOINABLE);
-
-            single_tcg_halt_cond = cpu->halt_cond;
-            single_tcg_cpu_thread = cpu->thread;
-        }
-#ifdef _WIN32
-        cpu->hThread = qemu_thread_get_handle(cpu->thread);
-#endif
-    } else {
-        /* For non-MTTCG cases we share the thread */
-        cpu->thread = single_tcg_cpu_thread;
-        cpu->halt_cond = single_tcg_halt_cond;
-        cpu->thread_id = first_cpu->thread_id;
-        cpu->can_do_io = 1;
-        cpu->created = true;
-    }
-}
-
-static void qemu_hax_start_vcpu(CPUState *cpu)
-{
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-
-    cpu->thread = g_malloc0(sizeof(QemuThread));
-    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-    qemu_cond_init(cpu->halt_cond);
-
-    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/HAX",
-             cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qemu_hax_cpu_thread_fn,
-                       cpu, QEMU_THREAD_JOINABLE);
-#ifdef _WIN32
-    cpu->hThread = qemu_thread_get_handle(cpu->thread);
-#endif
-}
-
-static void qemu_kvm_start_vcpu(CPUState *cpu)
+void cpus_register_accel(CpusAccel *i)
 {
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-
-    cpu->thread = g_malloc0(sizeof(QemuThread));
-    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-    qemu_cond_init(cpu->halt_cond);
-    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/KVM",
-             cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qemu_kvm_cpu_thread_fn,
-                       cpu, QEMU_THREAD_JOINABLE);
-}
-
-static void qemu_hvf_start_vcpu(CPUState *cpu)
-{
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-
-    /* HVF currently does not support TCG, and only runs in
-     * unrestricted-guest mode. */
-    assert(hvf_enabled());
-
-    cpu->thread = g_malloc0(sizeof(QemuThread));
-    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-    qemu_cond_init(cpu->halt_cond);
+    assert(i != NULL);
+    assert(i->create_vcpu_thread != NULL);
+    assert(i->kick_vcpu_thread != NULL);
 
-    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/HVF",
-             cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qemu_hvf_cpu_thread_fn,
-                       cpu, QEMU_THREAD_JOINABLE);
-}
-
-static void qemu_whpx_start_vcpu(CPUState *cpu)
-{
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-
-    cpu->thread = g_malloc0(sizeof(QemuThread));
-    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-    qemu_cond_init(cpu->halt_cond);
-    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/WHPX",
-             cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qemu_whpx_cpu_thread_fn,
-                       cpu, QEMU_THREAD_JOINABLE);
-#ifdef _WIN32
-    cpu->hThread = qemu_thread_get_handle(cpu->thread);
-#endif
-}
+    assert(i->synchronize_post_reset != NULL);
+    assert(i->synchronize_post_init != NULL);
+    assert(i->synchronize_state != NULL);
+    assert(i->synchronize_pre_loadvm != NULL);
 
-static void qemu_dummy_start_vcpu(CPUState *cpu)
-{
-    char thread_name[VCPU_THREAD_NAME_SIZE];
-
-    cpu->thread = g_malloc0(sizeof(QemuThread));
-    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
-    qemu_cond_init(cpu->halt_cond);
-    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/DUMMY",
-             cpu->cpu_index);
-    qemu_thread_create(cpu->thread, thread_name, qemu_dummy_cpu_thread_fn, cpu,
-                       QEMU_THREAD_JOINABLE);
+    cpus_accel = *i;
 }
 
 void qemu_init_vcpu(CPUState *cpu)
@@ -1309,19 +536,8 @@  void qemu_init_vcpu(CPUState *cpu)
         cpu_address_space_init(cpu, 0, "cpu-memory", cpu->memory);
     }
 
-    if (kvm_enabled()) {
-        qemu_kvm_start_vcpu(cpu);
-    } else if (hax_enabled()) {
-        qemu_hax_start_vcpu(cpu);
-    } else if (hvf_enabled()) {
-        qemu_hvf_start_vcpu(cpu);
-    } else if (tcg_enabled()) {
-        qemu_tcg_init_vcpu(cpu);
-    } else if (whpx_enabled()) {
-        qemu_whpx_start_vcpu(cpu);
-    } else {
-        qemu_dummy_start_vcpu(cpu);
-    }
+    assert(cpus_accel.create_vcpu_thread != NULL);
+    cpus_accel.create_vcpu_thread(cpu);
 
     while (!cpu->created) {
         qemu_cond_wait(&qemu_cpu_cond, &qemu_global_mutex);
@@ -1499,3 +715,26 @@  void qmp_inject_nmi(Error **errp)
     nmi_monitor_handle(monitor_get_cpu_index(), errp);
 }
 
+void cpu_synchronize_state(CPUState *cpu)
+{
+    assert(cpus_accel.synchronize_state != NULL);
+    cpus_accel.synchronize_state(cpu);
+}
+
+void cpu_synchronize_post_reset(CPUState *cpu)
+{
+    assert(cpus_accel.synchronize_post_reset != NULL);
+    cpus_accel.synchronize_post_reset(cpu);
+}
+
+void cpu_synchronize_post_init(CPUState *cpu)
+{
+    assert(cpus_accel.synchronize_post_init != NULL);
+    cpus_accel.synchronize_post_init(cpu);
+}
+
+void cpu_synchronize_pre_loadvm(CPUState *cpu)
+{
+    assert(cpus_accel.synchronize_pre_loadvm != NULL);
+    cpus_accel.synchronize_pre_loadvm(cpu);
+}
diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 08998f981e..9f5a5002c7 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -25,6 +25,7 @@  stub-obj-y += tpm.o
 stub-obj-y += trace-control.o
 stub-obj-y += vmstate.o
 stub-obj-$(CONFIG_SOFTMMU) += win32-kbd-hook.o
+stub-obj-y += cpu-synchronize-state.o
 
 #######################################################################
 # code used by both qemu system emulation and qemu-img
diff --git a/stubs/cpu-synchronize-state.c b/stubs/cpu-synchronize-state.c
new file mode 100644
index 0000000000..3112fe439d
--- /dev/null
+++ b/stubs/cpu-synchronize-state.c
@@ -0,0 +1,15 @@ 
+#include "qemu/osdep.h"
+#include "sysemu/hw_accel.h"
+
+void cpu_synchronize_state(CPUState *cpu)
+{
+}
+void cpu_synchronize_post_reset(CPUState *cpu)
+{
+}
+void cpu_synchronize_post_init(CPUState *cpu)
+{
+}
+void cpu_synchronize_pre_loadvm(CPUState *cpu)
+{
+}
diff --git a/target/i386/Makefile.objs b/target/i386/Makefile.objs
index 48e0c28434..8a086933bc 100644
--- a/target/i386/Makefile.objs
+++ b/target/i386/Makefile.objs
@@ -9,14 +9,15 @@  obj-y += machine.o arch_memory_mapping.o arch_dump.o monitor.o
 obj-$(CONFIG_KVM) += kvm.o
 obj-$(CONFIG_HYPERV) += hyperv.o
 obj-$(call lnot,$(CONFIG_HYPERV)) += hyperv-stub.o
+obj-$(CONFIG_HAX) += hax-all.o hax-mem.o hax-cpus.o
 ifeq ($(CONFIG_WIN32),y)
-obj-$(CONFIG_HAX) += hax-all.o hax-mem.o hax-windows.o
+obj-$(CONFIG_HAX) += hax-windows.o
 endif
 ifeq ($(CONFIG_POSIX),y)
-obj-$(CONFIG_HAX) += hax-all.o hax-mem.o hax-posix.o
+obj-$(CONFIG_HAX) += hax-posix.o
 endif
 obj-$(CONFIG_HVF) += hvf/
-obj-$(CONFIG_WHPX) += whpx-all.o
+obj-$(CONFIG_WHPX) += whpx-all.o whpx-cpus.o
 endif
 obj-$(CONFIG_SEV) += sev.o
 obj-$(call lnot,$(CONFIG_SEV)) += sev-stub.o
diff --git a/target/i386/hax-all.c b/target/i386/hax-all.c
index c93bb23a44..b66ddeb8bf 100644
--- a/target/i386/hax-all.c
+++ b/target/i386/hax-all.c
@@ -32,9 +32,10 @@ 
 #include "sysemu/accel.h"
 #include "sysemu/reset.h"
 #include "sysemu/runstate.h"
-#include "qemu/main-loop.h"
 #include "hw/boards.h"
 
+#include "hax-cpus.h"
+
 #define DEBUG_HAX 0
 
 #define DPRINTF(fmt, ...) \
@@ -374,6 +375,9 @@  static int hax_accel_init(MachineState *ms)
                 !ret ? "working" : "not working",
                 !ret ? "fast virt" : "emulation");
     }
+    if (ret == 0) {
+        cpus_register_accel(&hax_cpus);
+    }
     return ret;
 }
 
diff --git a/target/i386/hax-cpus.c b/target/i386/hax-cpus.c
new file mode 100644
index 0000000000..69a4162939
--- /dev/null
+++ b/target/i386/hax-cpus.c
@@ -0,0 +1,85 @@ 
+/*
+ * QEMU HAX support
+ *
+ * Copyright IBM, Corp. 2008
+ *           Red Hat, Inc. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Glauber Costa     <gcosta@redhat.com>
+ *
+ * Copyright (c) 2011 Intel Corporation
+ *  Written by:
+ *  Jiang Yunhong<yunhong.jiang@intel.com>
+ *  Xin Xiaohui<xiaohui.xin@intel.com>
+ *  Zhang Xiantao<xiantao.zhang@intel.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+#include "hax-i386.h"
+#include "sysemu/runstate.h"
+#include "sysemu/cpus.h"
+#include "qemu/guest-random.h"
+
+#include "hax-cpus.h"
+
+static void *hax_cpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+    int r;
+
+    rcu_register_thread();
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+
+    cpu->thread_id = qemu_get_thread_id();
+    hax_init_vcpu(cpu);
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    do {
+        if (cpu_can_run(cpu)) {
+            r = hax_smp_cpu_exec(cpu);
+            if (r == EXCP_DEBUG) {
+                cpu_handle_guest_debug(cpu);
+            }
+        }
+
+        qemu_wait_io_event(cpu);
+    } while (!cpu->unplug || cpu_can_run(cpu));
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static void hax_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+
+    cpu->thread = g_malloc0(sizeof(QemuThread));
+    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(cpu->halt_cond);
+
+    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/HAX",
+             cpu->cpu_index);
+    qemu_thread_create(cpu->thread, thread_name, hax_cpu_thread_fn,
+                       cpu, QEMU_THREAD_JOINABLE);
+#ifdef _WIN32
+    cpu->hThread = qemu_thread_get_handle(cpu->thread);
+#endif
+}
+
+CpusAccel hax_cpus = {
+    .create_vcpu_thread = hax_start_vcpu_thread,
+    .kick_vcpu_thread = hax_kick_vcpu_thread,
+
+    .synchronize_post_reset = hax_cpu_synchronize_post_reset,
+    .synchronize_post_init = hax_cpu_synchronize_post_init,
+    .synchronize_state = hax_cpu_synchronize_state,
+    .synchronize_pre_loadvm = hax_cpu_synchronize_pre_loadvm,
+};
diff --git a/target/i386/hax-cpus.h b/target/i386/hax-cpus.h
new file mode 100644
index 0000000000..ac3cf1f8ae
--- /dev/null
+++ b/target/i386/hax-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HAX_CPUS_H
+#define HAX_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel hax_cpus;
+
+#endif /* HAX_CPUS_H */
diff --git a/target/i386/hax-i386.h b/target/i386/hax-i386.h
index ec28708185..48c4abe14e 100644
--- a/target/i386/hax-i386.h
+++ b/target/i386/hax-i386.h
@@ -60,6 +60,8 @@  int hax_inject_interrupt(CPUArchState *env, int vector);
 struct hax_vm *hax_vm_create(struct hax_state *hax, int max_cpus);
 int hax_vcpu_run(struct hax_vcpu_state *vcpu);
 int hax_vcpu_create(int id);
+void hax_kick_vcpu_thread(CPUState *cpu);
+
 int hax_sync_vcpu_state(CPUArchState *env, struct vcpu_state_t *state,
                         int set);
 int hax_sync_msr(CPUArchState *env, struct hax_msr_data *msrs, int set);
diff --git a/target/i386/hax-posix.c b/target/i386/hax-posix.c
index 3bad89f133..ea956ddfc1 100644
--- a/target/i386/hax-posix.c
+++ b/target/i386/hax-posix.c
@@ -16,6 +16,8 @@ 
 
 #include "target/i386/hax-i386.h"
 
+#include "sysemu/cpus.h"
+
 hax_fd hax_mod_open(void)
 {
     int fd = open("/dev/HAX", O_RDWR);
@@ -292,3 +294,13 @@  int hax_inject_interrupt(CPUArchState *env, int vector)
 
     return ioctl(fd, HAX_VCPU_IOCTL_INTERRUPT, &vector);
 }
+
+void hax_kick_vcpu_thread(CPUState *cpu)
+{
+    /*
+     * FIXME: race condition with the exit_request check in
+     * hax_vcpu_hax_exec
+     */
+    cpu->exit_request = 1;
+    cpus_kick_thread(cpu);
+}
diff --git a/target/i386/hax-windows.c b/target/i386/hax-windows.c
index 863c2bcc19..469b48e608 100644
--- a/target/i386/hax-windows.c
+++ b/target/i386/hax-windows.c
@@ -463,3 +463,23 @@  int hax_inject_interrupt(CPUArchState *env, int vector)
         return 0;
     }
 }
+
+static void CALLBACK dummy_apc_func(ULONG_PTR unused)
+{
+}
+
+void hax_kick_vcpu_thread(CPUState *cpu)
+{
+    /*
+     * FIXME: race condition with the exit_request check in
+     * hax_vcpu_hax_exec
+     */
+    cpu->exit_request = 1;
+    if (!qemu_cpu_is_self(cpu)) {
+        if (!QueueUserAPC(dummy_apc_func, cpu->hThread, 0)) {
+            fprintf(stderr, "%s: QueueUserAPC failed with error %lu\n",
+                    __func__, GetLastError());
+            exit(1);
+        }
+    }
+}
diff --git a/target/i386/hvf/Makefile.objs b/target/i386/hvf/Makefile.objs
index 927b86bc67..af9f7dcfc1 100644
--- a/target/i386/hvf/Makefile.objs
+++ b/target/i386/hvf/Makefile.objs
@@ -1,2 +1,2 @@ 
-obj-y += hvf.o
+obj-y += hvf.o hvf-cpus.o
 obj-y += x86.o x86_cpuid.o x86_decode.o x86_descr.o x86_emu.o x86_flags.o x86_mmu.o x86hvf.o x86_task.o
diff --git a/target/i386/hvf/hvf-cpus.c b/target/i386/hvf/hvf-cpus.c
new file mode 100644
index 0000000000..a6970701c3
--- /dev/null
+++ b/target/i386/hvf/hvf-cpus.c
@@ -0,0 +1,141 @@ 
+/*
+ * Copyright 2008 IBM Corporation
+ *           2008 Red Hat, Inc.
+ * Copyright 2011 Intel Corporation
+ * Copyright 2016 Veertu, Inc.
+ * Copyright 2017 The Android Open Source Project
+ *
+ * QEMU Hypervisor.framework support
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * This file contain code under public domain from the hvdos project:
+ * https://github.com/mist64/hvdos
+ *
+ * Parts Copyright (c) 2011 NetApp, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+#include "sysemu/hvf.h"
+#include "sysemu/runstate.h"
+#include "target/i386/cpu.h"
+#include "qemu/guest-random.h"
+
+#include "hvf-cpus.h"
+
+/*
+ * The HVF-specific vCPU thread function. This one should only run when the host
+ * CPU supports the VMX "unrestricted guest" feature.
+ */
+static void *hvf_cpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+
+    int r;
+
+    assert(hvf_enabled());
+
+    rcu_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+
+    cpu->thread_id = qemu_get_thread_id();
+    cpu->can_do_io = 1;
+    current_cpu = cpu;
+
+    hvf_init_vcpu(cpu);
+
+    /* signal CPU creation */
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    do {
+        if (cpu_can_run(cpu)) {
+            r = hvf_vcpu_exec(cpu);
+            if (r == EXCP_DEBUG) {
+                cpu_handle_guest_debug(cpu);
+            }
+        }
+        qemu_wait_io_event(cpu);
+    } while (!cpu->unplug || cpu_can_run(cpu));
+
+    hvf_vcpu_destroy(cpu);
+    cpu_thread_signal_destroyed(cpu);
+    qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static void hvf_kick_vcpu_thread(CPUState *cpu)
+{
+    cpus_kick_thread(cpu);
+}
+
+static void hvf_cpu_synchronize_noop(CPUState *cpu)
+{
+}
+
+static void hvf_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+
+    /*
+     * HVF currently does not support TCG, and only runs in
+     * unrestricted-guest mode.
+     */
+    assert(hvf_enabled());
+
+    cpu->thread = g_malloc0(sizeof(QemuThread));
+    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(cpu->halt_cond);
+
+    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/HVF",
+             cpu->cpu_index);
+    qemu_thread_create(cpu->thread, thread_name, hvf_cpu_thread_fn,
+                       cpu, QEMU_THREAD_JOINABLE);
+}
+
+CpusAccel hvf_cpus = {
+    .create_vcpu_thread = hvf_start_vcpu_thread,
+    .kick_vcpu_thread = hvf_kick_vcpu_thread,
+
+    .synchronize_post_reset = hvf_cpu_synchronize_post_reset,
+    .synchronize_post_init = hvf_cpu_synchronize_post_init,
+    .synchronize_state = hvf_cpu_synchronize_state,
+    .synchronize_pre_loadvm = hvf_cpu_synchronize_noop,
+};
diff --git a/target/i386/hvf/hvf-cpus.h b/target/i386/hvf/hvf-cpus.h
new file mode 100644
index 0000000000..b66f4889b0
--- /dev/null
+++ b/target/i386/hvf/hvf-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef HVF_CPUS_H
+#define HVF_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel hvf_cpus;
+
+#endif /* HVF_CPUS_H */
diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
index be016b951a..23e5ee6048 100644
--- a/target/i386/hvf/hvf.c
+++ b/target/i386/hvf/hvf.c
@@ -72,6 +72,8 @@ 
 #include "sysemu/accel.h"
 #include "target/i386/cpu.h"
 
+#include "hvf-cpus.h"
+
 HVFState *hvf_state;
 
 static void assert_hvf_ok(hv_return_t ret)
@@ -977,6 +979,7 @@  static int hvf_accel_init(MachineState *ms)
     hvf_state = s;
     cpu_interrupt_handler = hvf_handle_interrupt;
     memory_listener_register(&hvf_memory_listener, &address_space_memory);
+    cpus_register_accel(&hvf_cpus);
     return 0;
 }
 
diff --git a/target/i386/whpx-all.c b/target/i386/whpx-all.c
index c78baac6df..8b6986c864 100644
--- a/target/i386/whpx-all.c
+++ b/target/i386/whpx-all.c
@@ -24,6 +24,8 @@ 
 #include "migration/blocker.h"
 #include "whp-dispatch.h"
 
+#include "whpx-cpus.h"
+
 #include <WinHvPlatform.h>
 #include <WinHvEmulation.h>
 
@@ -1575,6 +1577,7 @@  static int whpx_accel_init(MachineState *ms)
     whpx_memory_init();
 
     cpu_interrupt_handler = whpx_handle_interrupt;
+    cpus_register_accel(&whpx_cpus);
 
     printf("Windows Hypervisor Platform accelerator is operational\n");
     return 0;
diff --git a/target/i386/whpx-cpus.c b/target/i386/whpx-cpus.c
new file mode 100644
index 0000000000..3a0b69f771
--- /dev/null
+++ b/target/i386/whpx-cpus.c
@@ -0,0 +1,96 @@ 
+/*
+ * QEMU Windows Hypervisor Platform accelerator (WHPX)
+ *
+ * Copyright Microsoft Corp. 2017
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/kvm_int.h"
+#include "qemu/main-loop.h"
+#include "sysemu/cpus.h"
+#include "qemu/guest-random.h"
+
+#include "sysemu/whpx.h"
+#include "whpx-cpus.h"
+
+#include <WinHvPlatform.h>
+#include <WinHvEmulation.h>
+
+static void *whpx_cpu_thread_fn(void *arg)
+{
+    CPUState *cpu = arg;
+    int r;
+
+    rcu_register_thread();
+
+    qemu_mutex_lock_iothread();
+    qemu_thread_get_self(cpu->thread);
+    cpu->thread_id = qemu_get_thread_id();
+    current_cpu = cpu;
+
+    r = whpx_init_vcpu(cpu);
+    if (r < 0) {
+        fprintf(stderr, "whpx_init_vcpu failed: %s\n", strerror(-r));
+        exit(1);
+    }
+
+    /* signal CPU creation */
+    cpu_thread_signal_created(cpu);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
+
+    do {
+        if (cpu_can_run(cpu)) {
+            r = whpx_vcpu_exec(cpu);
+            if (r == EXCP_DEBUG) {
+                cpu_handle_guest_debug(cpu);
+            }
+        }
+        while (cpu_thread_is_idle(cpu)) {
+            qemu_cond_wait_iothread(cpu->halt_cond);
+        }
+        qemu_wait_io_event_common(cpu);
+    } while (!cpu->unplug || cpu_can_run(cpu));
+
+    whpx_destroy_vcpu(cpu);
+    cpu_thread_signal_destroyed(cpu);
+    qemu_mutex_unlock_iothread();
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static void whpx_start_vcpu_thread(CPUState *cpu)
+{
+    char thread_name[VCPU_THREAD_NAME_SIZE];
+
+    cpu->thread = g_malloc0(sizeof(QemuThread));
+    cpu->halt_cond = g_malloc0(sizeof(QemuCond));
+    qemu_cond_init(cpu->halt_cond);
+    snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/WHPX",
+             cpu->cpu_index);
+    qemu_thread_create(cpu->thread, thread_name, whpx_cpu_thread_fn,
+                       cpu, QEMU_THREAD_JOINABLE);
+#ifdef _WIN32
+    cpu->hThread = qemu_thread_get_handle(cpu->thread);
+#endif
+}
+
+static void whpx_kick_vcpu_thread(CPUState *cpu)
+{
+    if (!qemu_cpu_is_self(cpu)) {
+        whpx_vcpu_kick(cpu);
+    }
+}
+
+CpusAccel whpx_cpus = {
+    .create_vcpu_thread = whpx_start_vcpu_thread,
+    .kick_vcpu_thread = whpx_kick_vcpu_thread,
+
+    .synchronize_post_reset = whpx_cpu_synchronize_post_reset,
+    .synchronize_post_init = whpx_cpu_synchronize_post_init,
+    .synchronize_state = whpx_cpu_synchronize_state,
+    .synchronize_pre_loadvm = whpx_cpu_synchronize_pre_loadvm,
+};
diff --git a/target/i386/whpx-cpus.h b/target/i386/whpx-cpus.h
new file mode 100644
index 0000000000..60b7be3735
--- /dev/null
+++ b/target/i386/whpx-cpus.h
@@ -0,0 +1,17 @@ 
+/*
+ * Accelerator CPUS Interface
+ *
+ * Copyright 2020 SUSE LLC
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef WHPX_CPUS_H
+#define WHPX_CPUS_H
+
+#include "sysemu/cpus.h"
+
+extern CpusAccel whpx_cpus;
+
+#endif /* WHPX_CPUS_H */