Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs

From 9d5201975d2c9da4da8a945fcd9531c9fb2073c0 Mon Sep 17 00:00:00 2001
From: Will Auld <will.auld@intel.com>
Date: Wed, 12 Sep 2012 18:31:41 -0700
Subject: [PATCH] Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs

CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported

Basic design is to emulate the MSR by allowing reads and writes to the
hypervisor vcpu specific locations to store the value of the emulated MSRs.
In this way the IA32_TSC_ADJUST value will be included in all reads to
the TSC MSR whether through rdmsr or rdtsc.

As this is a new MSR that the guest may access and modify its value needs
to be migrated along with the other MRSs. The changes here are specifically
for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added
for migrating its value.
---
 target-i386/cpu.h     |    4 +++-
 target-i386/kvm.c     |   15 +++++++++++++++
 target-i386/machine.c |   21 +++++++++++++++++++++
 3 files changed, 39 insertions(+), 1 deletions(-)

On 2012-09-19 19:49, Auld, Will wrote:
> From 9d5201975d2c9da4da8a945fcd9531c9fb2073c0 Mon Sep 17 00:00:00 2001
> From: Will Auld <will.auld@intel.com>
> Date: Wed, 12 Sep 2012 18:31:41 -0700
> Subject: [PATCH] Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs
> 
> CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported
> 
> Basic design is to emulate the MSR by allowing reads and writes to the
> hypervisor vcpu specific locations to store the value of the emulated MSRs.
> In this way the IA32_TSC_ADJUST value will be included in all reads to
> the TSC MSR whether through rdmsr or rdtsc.
> 
> As this is a new MSR that the guest may access and modify its value needs
> to be migrated along with the other MRSs. The changes here are specifically
> for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added
> for migrating its value.
> ---
>  target-i386/cpu.h     |    4 +++-
>  target-i386/kvm.c     |   15 +++++++++++++++
>  target-i386/machine.c |   21 +++++++++++++++++++++
>  3 files changed, 39 insertions(+), 1 deletions(-)
> 
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index aabf993..7ca99c0 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -284,6 +284,7 @@
>  #define MSR_IA32_APICBASE_BSP           (1<<8)
>  #define MSR_IA32_APICBASE_ENABLE        (1<<11)
>  #define MSR_IA32_APICBASE_BASE          (0xfffff<<12)
> +#define MSR_TSC_ADJUST			0x0000003b
>  #define MSR_IA32_TSCDEADLINE            0x6e0
>  
>  #define MSR_MTRRcap			0xfe
> @@ -701,6 +702,7 @@ typedef struct CPUX86State {
>      uint64_t async_pf_en_msr;
>  
>      uint64_t tsc;
> +    uint64_t tsc_adjust;
>      uint64_t tsc_deadline;
>  
>      uint64_t mcg_status;
> @@ -979,7 +981,7 @@ static inline CPUX86State *cpu_init(const char *cpu_model)
>  #define cpu_list_id x86_cpu_list
>  #define cpudef_setup	x86_cpudef_setup
>  
> -#define CPU_SAVE_VERSION 12
> +#define CPU_SAVE_VERSION 13

That bump is not needed as you append the new field via a subsection.

Jan

>  
>  /* MMU modes definitions */
>  #define MMU_MODE0_SUFFIX _kernel
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 696b14a..e974c42 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -61,6 +61,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
>  
>  static bool has_msr_star;
>  static bool has_msr_hsave_pa;
> +static bool has_msr_tsc_adjust;
>  static bool has_msr_tsc_deadline;
>  static bool has_msr_async_pf_en;
>  static bool has_msr_misc_enable;
> @@ -641,6 +642,10 @@ static int kvm_get_supported_msrs(KVMState *s)
>                      has_msr_hsave_pa = true;
>                      continue;
>                  }
> +                if (kvm_msr_list->indices[i] == MSR_TSC_ADJUST) {
> +                    has_msr_tsc_adjust = true;
> +                    continue;
> +                }
>                  if (kvm_msr_list->indices[i] == MSR_IA32_TSCDEADLINE) {
>                      has_msr_tsc_deadline = true;
>                      continue;
> @@ -978,6 +983,10 @@ static int kvm_put_msrs(CPUX86State *env, int level)
>      if (has_msr_hsave_pa) {
>          kvm_msr_entry_set(&msrs[n++], MSR_VM_HSAVE_PA, env->vm_hsave);
>      }
> +    if (has_msr_tsc_adjust) {
> +        kvm_msr_entry_set(&msrs[n++],
> +			MSR_TSC_ADJUST, env->tsc_adjust);
> +    }
>      if (has_msr_tsc_deadline) {
>          kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSCDEADLINE, env->tsc_deadline);
>      }
> @@ -1234,6 +1243,9 @@ static int kvm_get_msrs(CPUX86State *env)
>      if (has_msr_hsave_pa) {
>          msrs[n++].index = MSR_VM_HSAVE_PA;
>      }
> +    if (has_msr_tsc_adjust) {
> +        msrs[n++].index = MSR_TSC_ADJUST;
> +    }
>      if (has_msr_tsc_deadline) {
>          msrs[n++].index = MSR_IA32_TSCDEADLINE;
>      }
> @@ -1308,6 +1320,9 @@ static int kvm_get_msrs(CPUX86State *env)
>          case MSR_IA32_TSC:
>              env->tsc = msrs[i].data;
>              break;
> +        case MSR_TSC_ADJUST:
> +            env->tsc_adjust = msrs[i].data;
> +            break;
>          case MSR_IA32_TSCDEADLINE:
>              env->tsc_deadline = msrs[i].data;
>              break;
> diff --git a/target-i386/machine.c b/target-i386/machine.c
> index a8be058..95bda9b 100644
> --- a/target-i386/machine.c
> +++ b/target-i386/machine.c
> @@ -310,6 +310,24 @@ static const VMStateDescription vmstate_fpop_ip_dp = {
>      }
>  };
>  
> +static bool tsc_adjust_needed(void *opaque)
> +{
> +    CPUX86State *cpu = opaque;
> +
> +    return cpu->tsc_adjust != 0;
> +}
> +
> +static const VMStateDescription vmstate_msr_tsc_adjust = {
> +    .name = "cpu/msr_tsc_adjust",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .minimum_version_id_old = 1,
> +    .fields      = (VMStateField []) {
> +        VMSTATE_UINT64(tsc_adjust, CPUX86State),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static bool tscdeadline_needed(void *opaque)
>  {
>      CPUX86State *env = opaque;
> @@ -457,6 +475,9 @@ static const VMStateDescription vmstate_cpu = {
>              .vmsd = &vmstate_fpop_ip_dp,
>              .needed = fpop_ip_dp_needed,
>          }, {
> +            .vmsd = &vmstate_msr_tsc_adjust,
> +            .needed = tsc_adjust_needed,
> +        }, {
>              .vmsd = &vmstate_msr_tscdeadline,
>              .needed = tscdeadline_needed,
>          }, {
>