Patchwork [ACPIHP,part1,1/4] ACPIHP: introduce a framework for ACPI based system device hotplug

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Submitter Jiang Liu
Date Nov. 3, 2012, 4:07 p.m.
Message ID <1351958865-24394-2-git-send-email-jiang.liu@huawei.com>
Download mbox | patch
Permalink /patch/196867/
State Not Applicable
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Comments

Jiang Liu - Nov. 3, 2012, 4:07 p.m.
Modern high-end servers may support advanced RAS features, such as
system device dynamic reconfiguration. On x86 and IA64 platforms,
system device means processor(CPU), memory device, PCI host bridge
and even computer node.

The ACPI specifications have provided standard interfaces between
firmware and OS to support device dynamic reconfiguraiton at runtime.
This patch series introduces a new framework for system device
dynamic reconfiguration based on ACPI specification, which will
replace current existing system device hotplug logic embedded in
ACPI processor/memory/container device drivers.

The new ACPI based hotplug framework is modelled after the PCI hotplug
architecture and target to achieve following goals:
1) Optimize device configuration order to achieve best performance for
   hot-added system devices. For best perforamnce, system device should
   be configured in order of memory -> CPU -> IOAPIC/IOMMU -> PCI HB.
2) Resolve dependencies among hotplug slots. You need first to remove
   the memory device before removing a physical processor if a
   hotpluggable memory device is connected to a hotpluggable physical
   processor.
3) Provide interface to cancel ongoing hotplug operations. It may take
   a very long time to remove a memory device, so provide interface to
   cancel the inprogress hotplug operations.
4) Support new advanced RAS features, such as socket/memory migration.
5) Provide better user interfaces to access the hotplug functionalities.
6) Provide a mechanism to detect hotplug slots by checking existence
   of ACPI _EJ0 method or by other hardware platform specific methods.
7) Unify the way to enumerate ACPI based hotplug slots. All hotplug
   slots will be enumerated by the enumeration driver (acpihp_slot),
   instead of by individual ACPI device drivers.
8) Unify the way to handle ACPI hotplug events. All ACPI hotplug events
   for system devices will be handled by a generic ACPI hotplug driver
   (acpihp_drv) instead of by individual ACPI device drivers.
9) Provide better error handling and error recovery.
10) Trigger hotplug events/operations by software. This feature is useful
   for hardware fault management and/or power saving.

The new framework is composed up of three major components:
1) A system device hotplug slot enumerator driver, which enumerates
   hotplug slots in the system and provides platform specific methods
   to control those slots.
2) A system device hotplug driver, which is a platform independent
   driver to manage all hotplug slots created by the slot enumerator.
   The hotplug driver implements a state machine for hotplug slots and
   provides user interfaces to manage hotplug slots.
3) Several ACPI device drivers to configure/unconfigure system devices
   at runtime.

To get rid of inter dependengcy between the slot enumerator and hotplug
driver, common code shared by them will be built into the kernel. The
shared code provides some helper routines and a device class named
acpihp_slot_class with following default sysfs properties:
	capabilities: RAS capabilities of the hotplug slot
	state: current state of the hotplug slot state machine
	status: current health status of the hotplug slot
	object: ACPI object corresponding to the hotplug slot

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Gaohuai Han <hangaohuai@huawei.com>
---
 drivers/acpi/Kconfig          |   13 +
 drivers/acpi/Makefile         |    2 +
 drivers/acpi/hotplug/Makefile |    6 +
 drivers/acpi/hotplug/acpihp.h |   32 +++
 drivers/acpi/hotplug/core.c   |  543 +++++++++++++++++++++++++++++++++++++++++
 include/acpi/acpi_hotplug.h   |  208 ++++++++++++++++
 6 files changed, 804 insertions(+)
 create mode 100644 drivers/acpi/hotplug/Makefile
 create mode 100644 drivers/acpi/hotplug/acpihp.h
 create mode 100644 drivers/acpi/hotplug/core.c
 create mode 100644 include/acpi/acpi_hotplug.h
Bjorn Helgaas - Nov. 5, 2012, 9:05 p.m.
On Sat, Nov 3, 2012 at 10:07 AM, Jiang Liu <liuj97@gmail.com> wrote:
> Modern high-end servers may support advanced RAS features, such as
> system device dynamic reconfiguration. On x86 and IA64 platforms,
> system device means processor(CPU), memory device, PCI host bridge
> and even computer node.
>
> The ACPI specifications have provided standard interfaces between
> firmware and OS to support device dynamic reconfiguraiton at runtime.
> This patch series introduces a new framework for system device
> dynamic reconfiguration based on ACPI specification, which will
> replace current existing system device hotplug logic embedded in
> ACPI processor/memory/container device drivers.
>
> The new ACPI based hotplug framework is modelled after the PCI hotplug
> architecture and target to achieve following goals:
> 1) Optimize device configuration order to achieve best performance for
>    hot-added system devices. For best perforamnce, system device should
>    be configured in order of memory -> CPU -> IOAPIC/IOMMU -> PCI HB.
> 2) Resolve dependencies among hotplug slots. You need first to remove
>    the memory device before removing a physical processor if a
>    hotpluggable memory device is connected to a hotpluggable physical
>    processor.

Doesn't the namespace already have a way to communicate these dependencies?

> 3) Provide interface to cancel ongoing hotplug operations. It may take
>    a very long time to remove a memory device, so provide interface to
>    cancel the inprogress hotplug operations.
> 4) Support new advanced RAS features, such as socket/memory migration.
> 5) Provide better user interfaces to access the hotplug functionalities.
> 6) Provide a mechanism to detect hotplug slots by checking existence
>    of ACPI _EJ0 method or by other hardware platform specific methods.

I don't know what "hotplug slot" means for ACPI.  ACPI allows hotplug
of arbitrary devices in the namespace, whether they have EJ0 or not.

> 7) Unify the way to enumerate ACPI based hotplug slots. All hotplug
>    slots will be enumerated by the enumeration driver (acpihp_slot),
>    instead of by individual ACPI device drivers.

Why do we need to enumerate these "slots" specifically?

I think this patch adds things in /sys.  It might help if you
described what they are.

> 8) Unify the way to handle ACPI hotplug events. All ACPI hotplug events
>    for system devices will be handled by a generic ACPI hotplug driver
>    (acpihp_drv) instead of by individual ACPI device drivers.
> 9) Provide better error handling and error recovery.
> 10) Trigger hotplug events/operations by software. This feature is useful
>    for hardware fault management and/or power saving.
>
> The new framework is composed up of three major components:
> 1) A system device hotplug slot enumerator driver, which enumerates
>    hotplug slots in the system and provides platform specific methods
>    to control those slots.
> 2) A system device hotplug driver, which is a platform independent
>    driver to manage all hotplug slots created by the slot enumerator.
>    The hotplug driver implements a state machine for hotplug slots and
>    provides user interfaces to manage hotplug slots.
> 3) Several ACPI device drivers to configure/unconfigure system devices
>    at runtime.
>
> To get rid of inter dependengcy between the slot enumerator and hotplug
> driver, common code shared by them will be built into the kernel. The
> shared code provides some helper routines and a device class named
> acpihp_slot_class with following default sysfs properties:
>         capabilities: RAS capabilities of the hotplug slot
>         state: current state of the hotplug slot state machine
>         status: current health status of the hotplug slot
>         object: ACPI object corresponding to the hotplug slot
>
> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> Signed-off-by: Gaohuai Han <hangaohuai@huawei.com>

...
> +static char *acpihp_dev_mem_ids[] = {
> +       "PNP0C80",
> +       NULL
> +};
> +
> +static char *acpihp_dev_pcihb_ids[] = {
> +       "PNP0A03",
> +       NULL
> +};

Why should this driver need to know about these PNP IDs?  We ought to
be able to support hotplug of any device in the namespace, no matter
what its ID.
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Jiang Liu - Nov. 6, 2012, 4:18 p.m.
Hi Bjorn,
	Thanks for your review and please refer to inlined comments below.

On 11/06/2012 05:05 AM, Bjorn Helgaas wrote:
> On Sat, Nov 3, 2012 at 10:07 AM, Jiang Liu <liuj97@gmail.com> wrote:
>> Modern high-end servers may support advanced RAS features, such as
>> system device dynamic reconfiguration. On x86 and IA64 platforms,
>> system device means processor(CPU), memory device, PCI host bridge
>> and even computer node.
>>
>> The ACPI specifications have provided standard interfaces between
>> firmware and OS to support device dynamic reconfiguraiton at runtime.
>> This patch series introduces a new framework for system device
>> dynamic reconfiguration based on ACPI specification, which will
>> replace current existing system device hotplug logic embedded in
>> ACPI processor/memory/container device drivers.
>>
>> The new ACPI based hotplug framework is modelled after the PCI hotplug
>> architecture and target to achieve following goals:
>> 1) Optimize device configuration order to achieve best performance for
>>    hot-added system devices. For best perforamnce, system device should
>>    be configured in order of memory -> CPU -> IOAPIC/IOMMU -> PCI HB.
>> 2) Resolve dependencies among hotplug slots. You need first to remove
>>    the memory device before removing a physical processor if a
>>    hotpluggable memory device is connected to a hotpluggable physical
>>    processor.
> 
> Doesn't the namespace already have a way to communicate these dependencies?
The namespace could could resolve most dependency issues, but there are still
several corner cases need special care.
1) On a typical Intel Nehalem/Westmere platform, an IOH will be connected to
two physical processors through QPI. The IOH depends on the two processors.
And the ACPI namespace is something like:
/_SB
    |_SCK0
    |_SCK1
    |_PCI1
2) For a large system composed up of multiple computer nodes, nodes may have
dependency on neighbors due to interconnect topology constraints.

So we need to resolve dependency by both evaluating _EDL and analyze ACPI
namespace topology.

>> 3) Provide interface to cancel ongoing hotplug operations. It may take
>>    a very long time to remove a memory device, so provide interface to
>>    cancel the inprogress hotplug operations.
>> 4) Support new advanced RAS features, such as socket/memory migration.
>> 5) Provide better user interfaces to access the hotplug functionalities.
>> 6) Provide a mechanism to detect hotplug slots by checking existence
>>    of ACPI _EJ0 method or by other hardware platform specific methods.
> 
> I don't know what "hotplug slot" means for ACPI.  ACPI allows hotplug
> of arbitrary devices in the namespace, whether they have EJ0 or not.
Here "hotplug" slot is an abstraction of receptacles where a group of
system devices could be attached to, or where we could control a group
of system devices. It's totally conceptual, may or may not has 
corresponding physical slots. For example,
1) a hotplug slot for a hotpluggable memory board has a physical slot.
2) a hotplug slot for a non-hotpluggable processor with power control
capability has no physical slot. (That means you may power on/off a
physical processor but can't hotplug it at runtime). This case is useful
for hardware partitioning.

Detecting hotplug slots by checking existence of _EJ0 is the default
but unreliable way. For a real high-end server with system device
hotplug capabilities should provide some static ACPI table to describe
hotplug slots/capabilities. There are some ongoing efforts for that from
Intel, but not in the public domain yet. So the hotplug slot enumeration
driver is designed to extensible:)

>> 7) Unify the way to enumerate ACPI based hotplug slots. All hotplug
>>    slots will be enumerated by the enumeration driver (acpihp_slot),
>>    instead of by individual ACPI device drivers.
> 
> Why do we need to enumerate these "slots" specifically?
> 
> I think this patch adds things in /sys.  It might help if you
> described what they are.
There's no standard way in ACPI5.0 to describe system device hotplug slots yet.
And we want to show user the system device hotplug capabilities even when there
is no device attached to a slot. In other word, user could now how much
devices they could connect to the system by hotplugging.

>> 8) Unify the way to handle ACPI hotplug events. All ACPI hotplug events
>>    for system devices will be handled by a generic ACPI hotplug driver
>>    (acpihp_drv) instead of by individual ACPI device drivers.
>> 9) Provide better error handling and error recovery.
>> 10) Trigger hotplug events/operations by software. This feature is useful
>>    for hardware fault management and/or power saving.
>>
>> The new framework is composed up of three major components:
>> 1) A system device hotplug slot enumerator driver, which enumerates
>>    hotplug slots in the system and provides platform specific methods
>>    to control those slots.
>> 2) A system device hotplug driver, which is a platform independent
>>    driver to manage all hotplug slots created by the slot enumerator.
>>    The hotplug driver implements a state machine for hotplug slots and
>>    provides user interfaces to manage hotplug slots.
>> 3) Several ACPI device drivers to configure/unconfigure system devices
>>    at runtime.
>>
>> To get rid of inter dependengcy between the slot enumerator and hotplug
>> driver, common code shared by them will be built into the kernel. The
>> shared code provides some helper routines and a device class named
>> acpihp_slot_class with following default sysfs properties:
>>         capabilities: RAS capabilities of the hotplug slot
>>         state: current state of the hotplug slot state machine
>>         status: current health status of the hotplug slot
>>         object: ACPI object corresponding to the hotplug slot
>>
>> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
>> Signed-off-by: Gaohuai Han <hangaohuai@huawei.com>
> 
> ...
>> +static char *acpihp_dev_mem_ids[] = {
>> +       "PNP0C80",
>> +       NULL
>> +};
>> +
>> +static char *acpihp_dev_pcihb_ids[] = {
>> +       "PNP0A03",
>> +       NULL
>> +};
> 
> Why should this driver need to know about these PNP IDs?  We ought to
> be able to support hotplug of any device in the namespace, no matter
> what its ID.
We need PNP IDs for:
1) Give a meaningful name for each slot.
lrwxrwxrwx  CPU00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00
lrwxrwxrwx  CPU01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01
lrwxrwxrwx  CPU02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02
lrwxrwxrwx  CPU03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03
lrwxrwxrwx  IOX01 -> ../../../devices/LNXSYSTM:00/acpihp/IOX01
lrwxrwxrwx  MEM00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM00
lrwxrwxrwx  MEM01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM01
lrwxrwxrwx  MEM02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM02
lrwxrwxrwx  MEM03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM03
lrwxrwxrwx  MEM04 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM04
lrwxrwxrwx  MEM05 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM05
lrwxrwxrwx  MEM06 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM06
lrwxrwxrwx  MEM07 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM07

2) Classify system device into groups according to device types, so we could
configure/unconfigure them in optimal order for performance as:
memory -> CPU -> IOAPIC -> PCI host bridge

3) The new hotplug framework are designed to handle system device hotplug,
and it won't hand IO device hotplug such as PCI etc. So it need to stop
scanning subtree of PCI host bridges.

Thanks!
Gerry
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Rafael J. Wysocki - Nov. 19, 2012, 8:43 a.m.
Hi,

On Wednesday, November 07, 2012 12:18:07 AM Jiang Liu wrote:
> Hi Bjorn,
> 	Thanks for your review and please refer to inlined comments below.
> 
> On 11/06/2012 05:05 AM, Bjorn Helgaas wrote:
> > On Sat, Nov 3, 2012 at 10:07 AM, Jiang Liu <liuj97@gmail.com> wrote:
> >> Modern high-end servers may support advanced RAS features, such as
> >> system device dynamic reconfiguration. On x86 and IA64 platforms,
> >> system device means processor(CPU), memory device, PCI host bridge
> >> and even computer node.
> >>
> >> The ACPI specifications have provided standard interfaces between
> >> firmware and OS to support device dynamic reconfiguraiton at runtime.
> >> This patch series introduces a new framework for system device
> >> dynamic reconfiguration based on ACPI specification, which will
> >> replace current existing system device hotplug logic embedded in
> >> ACPI processor/memory/container device drivers.
> >>
> >> The new ACPI based hotplug framework is modelled after the PCI hotplug
> >> architecture and target to achieve following goals:
> >> 1) Optimize device configuration order to achieve best performance for
> >>    hot-added system devices. For best perforamnce, system device should
> >>    be configured in order of memory -> CPU -> IOAPIC/IOMMU -> PCI HB.
> >> 2) Resolve dependencies among hotplug slots. You need first to remove
> >>    the memory device before removing a physical processor if a
> >>    hotpluggable memory device is connected to a hotpluggable physical
> >>    processor.
> > 
> > Doesn't the namespace already have a way to communicate these dependencies?

> The namespace could could resolve most dependency issues, but there are still
> several corner cases need special care.
> 1) On a typical Intel Nehalem/Westmere platform, an IOH will be connected to
> two physical processors through QPI. The IOH depends on the two processors.
> And the ACPI namespace is something like:
> /_SB
>     |_SCK0
>     |_SCK1
>     |_PCI1
> 2) For a large system composed up of multiple computer nodes, nodes may have
> dependency on neighbors due to interconnect topology constraints.
> 
> So we need to resolve dependency by both evaluating _EDL and analyze ACPI
> namespace topology.

Well, this doesn't explain why we need a new framework.

> >> 3) Provide interface to cancel ongoing hotplug operations. It may take
> >>    a very long time to remove a memory device, so provide interface to
> >>    cancel the inprogress hotplug operations.
> >> 4) Support new advanced RAS features, such as socket/memory migration.
> >> 5) Provide better user interfaces to access the hotplug functionalities.
> >> 6) Provide a mechanism to detect hotplug slots by checking existence
> >>    of ACPI _EJ0 method or by other hardware platform specific methods.
> > 
> > I don't know what "hotplug slot" means for ACPI.  ACPI allows hotplug
> > of arbitrary devices in the namespace, whether they have EJ0 or not.

> Here "hotplug" slot is an abstraction of receptacles where a group of
> system devices could be attached to, or where we could control a group
> of system devices. It's totally conceptual, may or may not has 
> corresponding physical slots.

Can that be called something different from "slot", then, to avoid confusion?

> For example,
> 1) a hotplug slot for a hotpluggable memory board has a physical slot.

So let's call that a "slot" and the abstraction above a "hotplug domain" or
something similar.  Because in fact we're talking about hotplug domains,
aren't we?

> 2) a hotplug slot for a non-hotpluggable processor with power control
> capability has no physical slot. (That means you may power on/off a
> physical processor but can't hotplug it at runtime). This case is useful
> for hardware partitioning.

People have been working on this particular thing for years, so I wonder
why you think that your apprach is going to be better here?

> Detecting hotplug slots by checking existence of _EJ0 is the default
> but unreliable way. For a real high-end server with system device
> hotplug capabilities should provide some static ACPI table to describe
> hotplug slots/capabilities. There are some ongoing efforts for that from
> Intel, but not in the public domain yet. So the hotplug slot enumeration
> driver is designed to extensible:)
> 
> >> 7) Unify the way to enumerate ACPI based hotplug slots. All hotplug
> >>    slots will be enumerated by the enumeration driver (acpihp_slot),
> >>    instead of by individual ACPI device drivers.
> > 
> > Why do we need to enumerate these "slots" specifically?
> > 
> > I think this patch adds things in /sys.  It might help if you
> > described what they are.

> There's no standard way in ACPI5.0 to describe system device hotplug slots yet.
> And we want to show user the system device hotplug capabilities even when there
> is no device attached to a slot. In other word, user could now how much
> devices they could connect to the system by hotplugging.

Bjorn probably meant "provide documentation describing the user space interfaces
being introduced".  Which in fact is a requirement.

> >> 8) Unify the way to handle ACPI hotplug events. All ACPI hotplug events
> >>    for system devices will be handled by a generic ACPI hotplug driver
> >>    (acpihp_drv) instead of by individual ACPI device drivers.
> >> 9) Provide better error handling and error recovery.
> >> 10) Trigger hotplug events/operations by software. This feature is useful
> >>    for hardware fault management and/or power saving.
> >>
> >> The new framework is composed up of three major components:
> >> 1) A system device hotplug slot enumerator driver, which enumerates
> >>    hotplug slots in the system and provides platform specific methods
> >>    to control those slots.
> >> 2) A system device hotplug driver, which is a platform independent
> >>    driver to manage all hotplug slots created by the slot enumerator.
> >>    The hotplug driver implements a state machine for hotplug slots and
> >>    provides user interfaces to manage hotplug slots.
> >> 3) Several ACPI device drivers to configure/unconfigure system devices
> >>    at runtime.
> >>
> >> To get rid of inter dependengcy between the slot enumerator and hotplug
> >> driver, common code shared by them will be built into the kernel. The
> >> shared code provides some helper routines and a device class named
> >> acpihp_slot_class with following default sysfs properties:
> >>         capabilities: RAS capabilities of the hotplug slot
> >>         state: current state of the hotplug slot state machine
> >>         status: current health status of the hotplug slot
> >>         object: ACPI object corresponding to the hotplug slot
> >>
> >> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
> >> Signed-off-by: Gaohuai Han <hangaohuai@huawei.com>
> > 
> > ...
> >> +static char *acpihp_dev_mem_ids[] = {
> >> +       "PNP0C80",
> >> +       NULL
> >> +};
> >> +
> >> +static char *acpihp_dev_pcihb_ids[] = {
> >> +       "PNP0A03",
> >> +       NULL
> >> +};
> > 
> > Why should this driver need to know about these PNP IDs?  We ought to
> > be able to support hotplug of any device in the namespace, no matter
> > what its ID.

> We need PNP IDs for:
> 1) Give a meaningful name for each slot.
> lrwxrwxrwx  CPU00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00
> lrwxrwxrwx  CPU01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01
> lrwxrwxrwx  CPU02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02
> lrwxrwxrwx  CPU03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03
> lrwxrwxrwx  IOX01 -> ../../../devices/LNXSYSTM:00/acpihp/IOX01
> lrwxrwxrwx  MEM00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM00
> lrwxrwxrwx  MEM01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM01
> lrwxrwxrwx  MEM02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM02
> lrwxrwxrwx  MEM03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM03
> lrwxrwxrwx  MEM04 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM04
> lrwxrwxrwx  MEM05 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM05
> lrwxrwxrwx  MEM06 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM06
> lrwxrwxrwx  MEM07 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM07
> 
> 2) Classify system device into groups according to device types, so we could
> configure/unconfigure them in optimal order for performance as:
> memory -> CPU -> IOAPIC -> PCI host bridge
> 
> 3) The new hotplug framework are designed to handle system device hotplug,
> and it won't hand IO device hotplug such as PCI etc. So it need to stop
> scanning subtree of PCI host bridges.

Well, we probably need a hotplug domains framework, which the thing you're
proposing seems to be.  However, the question is: Why should it cover "system
devices" only?

To me, it looks like such a framework should cover all hotplug devices in the
system, or at least all ACPI-based hotplug devices.

Thanks,
Rafael
Jiang Liu - Nov. 19, 2012, 3:57 p.m.
Hi Rafael,
	Thanks for your comments! And please refer to inlined comments below.

On 11/19/2012 04:43 PM, Rafael J. Wysocki wrote:
> Hi,
> 
> On Wednesday, November 07, 2012 12:18:07 AM Jiang Liu wrote:
>> Hi Bjorn,
>> 	Thanks for your review and please refer to inlined comments below.
>>
>> On 11/06/2012 05:05 AM, Bjorn Helgaas wrote:
>>> On Sat, Nov 3, 2012 at 10:07 AM, Jiang Liu <liuj97@gmail.com> wrote:
>>>> Modern high-end servers may support advanced RAS features, such as
>>>> system device dynamic reconfiguration. On x86 and IA64 platforms,
>>>> system device means processor(CPU), memory device, PCI host bridge
>>>> and even computer node.
>>>>
>>>> The ACPI specifications have provided standard interfaces between
>>>> firmware and OS to support device dynamic reconfiguraiton at runtime.
>>>> This patch series introduces a new framework for system device
>>>> dynamic reconfiguration based on ACPI specification, which will
>>>> replace current existing system device hotplug logic embedded in
>>>> ACPI processor/memory/container device drivers.
>>>>
>>>> The new ACPI based hotplug framework is modelled after the PCI hotplug
>>>> architecture and target to achieve following goals:
>>>> 1) Optimize device configuration order to achieve best performance for
>>>>    hot-added system devices. For best perforamnce, system device should
>>>>    be configured in order of memory -> CPU -> IOAPIC/IOMMU -> PCI HB.
>>>> 2) Resolve dependencies among hotplug slots. You need first to remove
>>>>    the memory device before removing a physical processor if a
>>>>    hotpluggable memory device is connected to a hotpluggable physical
>>>>    processor.
>>>
>>> Doesn't the namespace already have a way to communicate these dependencies?
> 
>> The namespace could could resolve most dependency issues, but there are still
>> several corner cases need special care.
>> 1) On a typical Intel Nehalem/Westmere platform, an IOH will be connected to
>> two physical processors through QPI. The IOH depends on the two processors.
>> And the ACPI namespace is something like:
>> /_SB
>>     |_SCK0
>>     |_SCK1
>>     |_PCI1
>> 2) For a large system composed up of multiple computer nodes, nodes may have
>> dependency on neighbors due to interconnect topology constraints.
>>
>> So we need to resolve dependency by both evaluating _EDL and analyze ACPI
>> namespace topology.
> 
> Well, this doesn't explain why we need a new framework.
Currently hotplug capable system devices are managed by different ACPI drivers,
such as processor, container and acpi_memhotplug. And these ACPI drivers only
know hotplug-capable devices managed by itself and don't know hotplug-capable
devices managed by other drivers. For example, ACPI processor driver doesn't
know hotplug memory devices. So existing ACPI system device hotplug drivers
don't resolve dependencies at all.

With the new framework, it knows all hotplug domains within the system, and
it will automatically resolves dependencies when changing state of a hotplug
domain. This is very important because hotplug requests may be triggered
concurrently through different mechanism, such pressing the hotplug button,
issued from OS or issued from the OOB system management center. The new
framework will guarantee that all requests are correctly serialized. 

>>>> 3) Provide interface to cancel ongoing hotplug operations. It may take
>>>>    a very long time to remove a memory device, so provide interface to
>>>>    cancel the inprogress hotplug operations.
>>>> 4) Support new advanced RAS features, such as socket/memory migration.
>>>> 5) Provide better user interfaces to access the hotplug functionalities.
>>>> 6) Provide a mechanism to detect hotplug slots by checking existence
>>>>    of ACPI _EJ0 method or by other hardware platform specific methods.
>>>
>>> I don't know what "hotplug slot" means for ACPI.  ACPI allows hotplug
>>> of arbitrary devices in the namespace, whether they have EJ0 or not.
> 
>> Here "hotplug" slot is an abstraction of receptacles where a group of
>> system devices could be attached to, or where we could control a group
>> of system devices. It's totally conceptual, may or may not has 
>> corresponding physical slots.
> 
> Can that be called something different from "slot", then, to avoid confusion?
On some other OSes, it's called "attachment point" or "AP". I use slot
because its used by PCI hotplug. If that causes confusion, we may call
it something else, any suggestion?

>> For example,
>> 1) a hotplug slot for a hotpluggable memory board has a physical slot.
> 
> So let's call that a "slot" and the abstraction above a "hotplug domain" or
> something similar.  Because in fact we're talking about hotplug domains,
> aren't we?
Yeah, maybe "hotplug domain" is a good candidate for "hotplug slot".

>> 2) a hotplug slot for a non-hotpluggable processor with power control
>> capability has no physical slot. (That means you may power on/off a
>> physical processor but can't hotplug it at runtime). This case is useful
>> for hardware partitioning.
> 
> People have been working on this particular thing for years, so I wonder
> why you think that your apprach is going to be better here?
To support hardware partitioning or power management, OS needs to provide
interfaces to control those power-control-capable devices. But currently
we have only interface to power off a device and without interface to
power on a device.

Another benefit of the new framework is to support memory migration. A memory
device may support memory migration but don't support memory hotplug. The
new framework will abstract the migration-capable memory device as a hotplug
domain, so user can manage the memory device.

>> Detecting hotplug slots by checking existence of _EJ0 is the default
>> but unreliable way. For a real high-end server with system device
>> hotplug capabilities should provide some static ACPI table to describe
>> hotplug slots/capabilities. There are some ongoing efforts for that from
>> Intel, but not in the public domain yet. So the hotplug slot enumeration
>> driver is designed to extensible:)
>>
>>>> 7) Unify the way to enumerate ACPI based hotplug slots. All hotplug
>>>>    slots will be enumerated by the enumeration driver (acpihp_slot),
>>>>    instead of by individual ACPI device drivers.
>>>
>>> Why do we need to enumerate these "slots" specifically?
>>>
>>> I think this patch adds things in /sys.  It might help if you
>>> described what they are.
> 
>> There's no standard way in ACPI5.0 to describe system device hotplug slots yet.
>> And we want to show user the system device hotplug capabilities even when there
>> is no device attached to a slot. In other word, user could now how much
>> devices they could connect to the system by hotplugging.
> 
> Bjorn probably meant "provide documentation describing the user space interfaces
> being introduced".  Which in fact is a requirement.
Thanks for reminder. Documentation for sysfs interface is a must, and we have
plan for that. How about providing sysfs interface docs after we have settled
down about the overall idea and design?

>>>> 8) Unify the way to handle ACPI hotplug events. All ACPI hotplug events
>>>>    for system devices will be handled by a generic ACPI hotplug driver
>>>>    (acpihp_drv) instead of by individual ACPI device drivers.
>>>> 9) Provide better error handling and error recovery.
>>>> 10) Trigger hotplug events/operations by software. This feature is useful
>>>>    for hardware fault management and/or power saving.
>>>>
>>>> The new framework is composed up of three major components:
>>>> 1) A system device hotplug slot enumerator driver, which enumerates
>>>>    hotplug slots in the system and provides platform specific methods
>>>>    to control those slots.
>>>> 2) A system device hotplug driver, which is a platform independent
>>>>    driver to manage all hotplug slots created by the slot enumerator.
>>>>    The hotplug driver implements a state machine for hotplug slots and
>>>>    provides user interfaces to manage hotplug slots.
>>>> 3) Several ACPI device drivers to configure/unconfigure system devices
>>>>    at runtime.
>>>>
>>>> To get rid of inter dependengcy between the slot enumerator and hotplug
>>>> driver, common code shared by them will be built into the kernel. The
>>>> shared code provides some helper routines and a device class named
>>>> acpihp_slot_class with following default sysfs properties:
>>>>         capabilities: RAS capabilities of the hotplug slot
>>>>         state: current state of the hotplug slot state machine
>>>>         status: current health status of the hotplug slot
>>>>         object: ACPI object corresponding to the hotplug slot
>>>>
>>>> Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
>>>> Signed-off-by: Gaohuai Han <hangaohuai@huawei.com>
>>>
>>> ...
>>>> +static char *acpihp_dev_mem_ids[] = {
>>>> +       "PNP0C80",
>>>> +       NULL
>>>> +};
>>>> +
>>>> +static char *acpihp_dev_pcihb_ids[] = {
>>>> +       "PNP0A03",
>>>> +       NULL
>>>> +};
>>>
>>> Why should this driver need to know about these PNP IDs?  We ought to
>>> be able to support hotplug of any device in the namespace, no matter
>>> what its ID.
> 
>> We need PNP IDs for:
>> 1) Give a meaningful name for each slot.
>> lrwxrwxrwx  CPU00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00
>> lrwxrwxrwx  CPU01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01
>> lrwxrwxrwx  CPU02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02
>> lrwxrwxrwx  CPU03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03
>> lrwxrwxrwx  IOX01 -> ../../../devices/LNXSYSTM:00/acpihp/IOX01
>> lrwxrwxrwx  MEM00 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM00
>> lrwxrwxrwx  MEM01 -> ../../../devices/LNXSYSTM:00/acpihp/CPU00/MEM01
>> lrwxrwxrwx  MEM02 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM02
>> lrwxrwxrwx  MEM03 -> ../../../devices/LNXSYSTM:00/acpihp/CPU01/MEM03
>> lrwxrwxrwx  MEM04 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM04
>> lrwxrwxrwx  MEM05 -> ../../../devices/LNXSYSTM:00/acpihp/CPU02/MEM05
>> lrwxrwxrwx  MEM06 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM06
>> lrwxrwxrwx  MEM07 -> ../../../devices/LNXSYSTM:00/acpihp/CPU03/MEM07
>>
>> 2) Classify system device into groups according to device types, so we could
>> configure/unconfigure them in optimal order for performance as:
>> memory -> CPU -> IOAPIC -> PCI host bridge
>>
>> 3) The new hotplug framework are designed to handle system device hotplug,
>> and it won't hand IO device hotplug such as PCI etc. So it need to stop
>> scanning subtree of PCI host bridges.
> 
> Well, we probably need a hotplug domains framework, which the thing you're
> proposing seems to be.  However, the question is: Why should it cover "system
> devices" only?
> 
> To me, it looks like such a framework should cover all hotplug devices in the
> system, or at least all ACPI-based hotplug devices.
It will be great if we could provide a framework for all types of devices,
including both system devices and IO devices. But when starting the ACPI
based system device hotplug project, we found almost all hotplug capable
IO buses/devices have already provided hotplug support, so we focused
on system device hotplug because it's still incomplete.

According to my experience, it's really convenient if OS could provide a
unified tool/interface to support both system device and io device hotplug,
with consistent commands and outputs. But it's hard to provide a framework
to support both system device and io device hotplug at kernel level.
And an example system's hotplug framework is composed up with:
1) a hotplug driver for each type of devices, such as USB, SCSI, PCI and
   system device.
2) a unified userspace application/interface to support all types of hotplug
   drivers

So with that in mind, we have designed the ACPI based system device hotplug
framework as a hotplug driver for system devices. And we still lack of a 
unified userspace application/interface to support all types of device hotplug.

Thanks
Gerry
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Patch

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 119d58d..9577b23 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -321,6 +321,19 @@  config X86_PM_TIMER
 	  You should nearly always say Y here because many modern
 	  systems require this timer. 
 
+menuconfig ACPI_HOTPLUG
+	bool "System Device Hotplug"
+	depends on (X86 || IA64) && SYSFS
+	default n
+	help
+	  This option enables a framework to dynamically reconfigure system
+	  devices at runtime based on ACPI specifications. On x86 and IA64
+	  platforms, system device includes processor(CPU), memory device,
+	  PCI/PCIe host bridge and computer node etc.
+
+	  If your hardware platform does not support system device dynamic
+	  reconfiguration at runtime, you need not to enable this option.
+
 config ACPI_CONTAINER
 	tristate "Container and Module Devices (EXPERIMENTAL)"
 	depends on EXPERIMENTAL
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 47199e2..17bea6c 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -73,3 +73,5 @@  obj-$(CONFIG_ACPI_PROCESSOR_AGGREGATOR) += acpi_pad.o
 obj-$(CONFIG_ACPI_IPMI)		+= acpi_ipmi.o
 
 obj-$(CONFIG_ACPI_APEI)		+= apei/
+
+obj-$(CONFIG_ACPI_HOTPLUG)	+= hotplug/
diff --git a/drivers/acpi/hotplug/Makefile b/drivers/acpi/hotplug/Makefile
new file mode 100644
index 0000000..5e7790f
--- /dev/null
+++ b/drivers/acpi/hotplug/Makefile
@@ -0,0 +1,6 @@ 
+#
+# Makefile for ACPI based system device hotplug drivers
+#
+
+obj-$(CONFIG_ACPI_HOTPLUG)			+= acpihp.o
+acpihp-y					= core.o
diff --git a/drivers/acpi/hotplug/acpihp.h b/drivers/acpi/hotplug/acpihp.h
new file mode 100644
index 0000000..7467895
--- /dev/null
+++ b/drivers/acpi/hotplug/acpihp.h
@@ -0,0 +1,32 @@ 
+/*
+ * Copyright (C) 2012 Huawei Tech. Co., Ltd.
+ * Copyright (C) 2012 Jiang Liu <jiang.liu@huawei.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#ifndef	ACPIHP_INTERNAL_H
+#define	ACPIHP_INTERNAL_H
+#include <acpi/acpi.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_hotplug.h>
+
+extern struct acpi_device *acpi_root;
+
+#endif
diff --git a/drivers/acpi/hotplug/core.c b/drivers/acpi/hotplug/core.c
new file mode 100644
index 0000000..c835a97
--- /dev/null
+++ b/drivers/acpi/hotplug/core.c
@@ -0,0 +1,543 @@ 
+/*
+ * Copyright (C) 2012 Huawei Tech. Co., Ltd.
+ * Copyright (C) 2012 Jiang Liu <jiang.liu@huawei.com>
+ * Copyright (C) 2012 Gaohuai Han <hangaohuai@huawei.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/bug.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/sem.h>
+#include <linux/version.h>
+#include <acpi/acpi.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_hotplug.h>
+#include "acpihp.h"
+
+#define to_acpihp_slot(d) container_of(d, struct acpihp_slot, dev)
+
+static DEFINE_MUTEX(acpihp_mutex);
+static int acpihp_class_count;
+static struct kset *acpihp_slot_kset;
+
+static char *acpihp_slot_names[ACPIHP_SLOT_TYPE_MAX] = {
+	[ACPIHP_SLOT_TYPE_UNKNOWN]	= "UNKNOWN",
+	[ACPIHP_SLOT_TYPE_COMMON]	= "SLOT",
+	[ACPIHP_SLOT_TYPE_NODE]		= "NODE",
+	[ACPIHP_SLOT_TYPE_SYSTEM_BOARD]	= "SB",
+	[ACPIHP_SLOT_TYPE_CPU]		= "CPU",
+	[ACPIHP_SLOT_TYPE_MEM]		= "MEM",
+	[ACPIHP_SLOT_TYPE_IOX]		= "IOX",
+};
+
+static char *acpihp_slot_states[] = {
+	[ACPIHP_SLOT_STATE_UNKNOWN]		= "unknown",
+	[ACPIHP_SLOT_STATE_ABSENT]		= "absent",
+	[ACPIHP_SLOT_STATE_PRESENT]		= "present",
+	[ACPIHP_SLOT_STATE_POWERED]		= "powered",
+	[ACPIHP_SLOT_STATE_CONNECTED]		= "connected",
+	[ACPIHP_SLOT_STATE_CONFIGURED]		= "configured",
+	[ACPIHP_SLOT_STATE_POWERING_ON]		= "powering on",
+	[ACPIHP_SLOT_STATE_POWERING_OFF]	= "powering off",
+	[ACPIHP_SLOT_STATE_CONNECTING]		= "connecting",
+	[ACPIHP_SLOT_STATE_DISCONNECTING]	= "disconneting",
+	[ACPIHP_SLOT_STATE_CONFIGURING]		= "configuring",
+	[ACPIHP_SLOT_STATE_UNCONFIGURING]	= "unconfiguring",
+};
+
+static char *acpihp_slot_status[] = {
+	"ok",
+	"irremovable",
+	"fault",
+	"irremovable, fault",
+};
+
+static char *acpihp_dev_container_ids[] = {
+	"ACPI0004",
+	"PNP0A05",
+	"PNP0A06",
+	NULL
+};
+
+static char *acpihp_dev_cpu_ids[] = {
+	"ACPI0007",
+	"LNXCPU",
+	NULL
+};
+
+static char *acpihp_dev_mem_ids[] = {
+	"PNP0C80",
+	NULL
+};
+
+static char *acpihp_dev_pcihb_ids[] = {
+	"PNP0A03",
+	NULL
+};
+
+static void acpihp_slot_release(struct device *dev)
+{
+	struct acpihp_slot *slot = to_acpihp_slot(dev);
+
+	kfree(slot);
+}
+
+/**
+ * acpihp_alloc_slot - allocate a hotplug slot for @handle
+ * @handle: the ACPI device handle to associated with the hotplug slot
+ * @name: optional name for the hotplug slot
+ *
+ * The returned data structure must be freed by calling acpihp_slot_put()
+ * instead of kfree().
+ */
+struct acpihp_slot *acpihp_alloc_slot(acpi_handle handle, char *name)
+{
+	struct acpihp_slot *slot;
+
+	if (name && strlen(name) >= ACPIHP_SLOT_NAME_MAX_SIZE) {
+		ACPIHP_DEBUG("slot name '%s' is too big.\n", name);
+		return NULL;
+	}
+
+	slot = kzalloc(sizeof(*slot), GFP_KERNEL);
+	if (slot == NULL) {
+		ACPIHP_DEBUG("fails to allocate memory for slot device.\n");
+		return NULL;
+	}
+
+	slot->handle = handle;
+	INIT_LIST_HEAD(&slot->slot_list);
+	INIT_LIST_HEAD(&slot->drvdata_list);
+	if (name)
+		strncpy(slot->name, name, sizeof(slot->name) - 1);
+	mutex_init(&slot->slot_mutex);
+
+	slot->dev.class = &acpihp_slot_class;
+	device_initialize(&slot->dev);
+
+	return slot;
+}
+EXPORT_SYMBOL_GPL(acpihp_alloc_slot);
+
+int acpihp_register_slot(struct acpihp_slot *slot)
+{
+	int ret;
+
+	if (!slot || !slot->slot_ops)
+		return -EINVAL;
+
+	/* Use ACPI root device to host top level hotplug slots */
+	if (slot->parent)
+		slot->dev.parent = &slot->parent->dev;
+	else
+		slot->dev.parent = &acpi_root->dev;
+
+	ret = device_add(&slot->dev);
+	if (!ret) {
+		slot->flags |= ACPIHP_SLOT_FLAG_REGISTERED;
+		if (sysfs_create_link(&acpihp_slot_kset->kobj, &slot->dev.kobj,
+				      slot->name))
+			dev_warn(&slot->dev, "fails to create symlink.\n");
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(acpihp_register_slot);
+
+void acpihp_unregister_slot(struct acpihp_slot *slot)
+{
+	if (slot && (slot->flags & ACPIHP_SLOT_FLAG_REGISTERED)) {
+		sysfs_remove_link(&acpihp_slot_kset->kobj, slot->name);
+		device_del(&slot->dev);
+		slot->flags &= ~ACPIHP_SLOT_FLAG_REGISTERED;
+	}
+}
+EXPORT_SYMBOL_GPL(acpihp_unregister_slot);
+
+struct acpihp_slot *acpihp_slot_get(struct acpihp_slot *slot)
+{
+	if (slot)
+		get_device(&slot->dev);
+
+	return slot;
+}
+EXPORT_SYMBOL_GPL(acpihp_slot_get);
+
+void acpihp_slot_put(struct acpihp_slot *slot)
+{
+	if (slot)
+		put_device(&slot->dev);
+}
+EXPORT_SYMBOL_GPL(acpihp_slot_put);
+
+static void acpihp_slot_data_handler(acpi_handle handle, void *context)
+{
+	return;
+}
+
+/* Bind the slot device to corresponding ACPI object handle */
+acpi_status acpihp_mark_slot(acpi_handle handle, struct acpihp_slot *slot)
+{
+	acpi_status status;
+
+	mutex_lock(&acpihp_mutex);
+	status = acpi_attach_data(handle, &acpihp_slot_data_handler, slot);
+	mutex_unlock(&acpihp_mutex);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(acpihp_mark_slot);
+
+acpi_status acpihp_unmark_slot(acpi_handle handle)
+{
+	acpi_status result;
+
+	mutex_lock(&acpihp_mutex);
+	result = acpi_detach_data(handle, &acpihp_slot_data_handler);
+	if (result == AE_NOT_FOUND)
+		result = AE_OK;
+	BUG_ON(result != AE_OK);
+	mutex_unlock(&acpihp_mutex);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(acpihp_unmark_slot);
+
+bool acpihp_is_slot(acpi_handle handle)
+{
+	acpi_status result;
+	void *data = NULL;
+
+	result = acpi_get_data(handle, &acpihp_slot_data_handler, &data);
+	BUG_ON(result != AE_OK && result != AE_NOT_FOUND);
+
+	return (result == AE_OK);
+}
+EXPORT_SYMBOL_GPL(acpihp_is_slot);
+
+struct acpihp_slot *acpihp_get_slot(acpi_handle handle)
+{
+	acpi_status result;
+	void *data = NULL;
+	struct acpihp_slot *slot = NULL;
+
+	mutex_lock(&acpihp_mutex);
+	result = acpi_get_data(handle, &acpihp_slot_data_handler, &data);
+	if (ACPI_SUCCESS(result) && data) {
+		slot = data;
+		acpihp_slot_get(slot);
+	}
+	mutex_unlock(&acpihp_mutex);
+
+	return slot;
+}
+EXPORT_SYMBOL_GPL(acpihp_get_slot);
+
+bool acpihp_dev_match_ids(struct acpi_device_info *infop, char **ids)
+{
+	int i, j;
+	struct acpica_device_id_list *cid_list;
+
+	if (infop == NULL || ids == NULL) {
+		ACPIHP_DEBUG("invalid parameters.\n");
+		return false;
+	}
+
+	if (infop->valid & ACPI_VALID_HID) {
+		for (i = 0; ids[i]; i++) {
+			if (strncmp(ids[i], infop->hardware_id.string,
+				    infop->hardware_id.length) == 0) {
+				return true;
+			}
+		}
+	}
+
+	if (infop->valid & ACPI_VALID_CID) {
+		for (i = 0; ids[i]; i++) {
+			cid_list = &infop->compatible_id_list;
+			for (j = 0; j < cid_list->count; j++) {
+				if (strncmp(ids[i],
+					    cid_list->ids[j].string,
+					    cid_list->ids[j].length) == 0) {
+						return true;
+				}
+			}
+		}
+	}
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(acpihp_dev_match_ids);
+
+int acpihp_dev_get_type(acpi_handle handle, enum acpihp_dev_type *type)
+{
+	struct acpi_device_info *infop = NULL;
+
+	if (handle == NULL || type == NULL) {
+		ACPIHP_DEBUG("invalid parameters.\n");
+		return -EINVAL;
+	}
+	if (ACPI_FAILURE(acpi_get_object_info(handle, &infop)))
+		return -ENODEV;
+
+	*type = ACPIHP_DEV_TYPE_UNKNOWN;
+	if (infop->type == ACPI_TYPE_PROCESSOR) {
+		*type = ACPIHP_DEV_TYPE_CPU;
+	} else if (infop->type == ACPI_TYPE_DEVICE) {
+		if (acpihp_dev_match_ids(infop, acpihp_dev_container_ids))
+			*type = ACPIHP_DEV_TYPE_CONTAINER;
+		else if (acpihp_dev_match_ids(infop, acpihp_dev_cpu_ids))
+			*type = ACPIHP_DEV_TYPE_CPU;
+		else if (acpihp_dev_match_ids(infop, acpihp_dev_mem_ids))
+			*type = ACPIHP_DEV_TYPE_MEM;
+		else if (acpihp_dev_match_ids(infop, acpihp_dev_pcihb_ids))
+			*type = ACPIHP_DEV_TYPE_HOST_BRIDGE;
+		else if ((infop->valid & (ACPI_VALID_ADR | ACPI_VALID_HID |
+			 ACPI_VALID_CID)) == ACPI_VALID_ADR)
+			*type = ACPIHP_DEV_TYPE_MAX;
+	}
+	kfree(infop);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpihp_dev_get_type);
+
+char *acpihp_get_slot_type_name(enum acpihp_slot_type type)
+{
+	if (type < 0 || type >= ACPIHP_SLOT_TYPE_MAX) {
+		ACPIHP_DEBUG("invalid parameters.\n");
+		return "UNKNOWN";
+	}
+
+	return acpihp_slot_names[type];
+}
+EXPORT_SYMBOL_GPL(acpihp_get_slot_type_name);
+
+acpi_status acpihp_slot_get_status(struct acpihp_slot *slot, u64 *status)
+{
+	acpi_status rc;
+
+	if (slot == NULL || status == NULL) {
+		ACPIHP_DEBUG("invalid parameters.\n");
+		return AE_BAD_PARAMETER;
+	} else if (slot->slot_ops == NULL) {
+		ACPIHP_SLOT_DEBUG(slot, "operation not supported.\n");
+		return AE_SUPPORT;
+	} else if (slot->slot_ops->get_status)
+		return slot->slot_ops->get_status(slot, status);
+
+	rc = acpi_evaluate_integer(slot->handle, METHOD_NAME__STA,
+				   NULL, status);
+	if (rc == AE_NOT_FOUND) {
+		*status = ACPI_STA_DEVICE_PRESENT | ACPI_STA_DEVICE_ENABLED |
+			  ACPI_STA_DEVICE_FUNCTIONING;
+		rc = AE_OK;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(acpihp_slot_get_status);
+
+acpi_status acpihp_slot_poweron(struct acpihp_slot *slot)
+{
+	if (slot == NULL) {
+		ACPIHP_DEBUG("invalid parameter.\n");
+		return AE_BAD_PARAMETER;
+	} else if (slot->slot_ops == NULL || slot->slot_ops->poweron == NULL) {
+		ACPIHP_SLOT_DEBUG(slot, "operation not supported.\n");
+		return AE_SUPPORT;
+	}
+
+	return slot->slot_ops->poweron(slot->handle);
+}
+EXPORT_SYMBOL_GPL(acpihp_slot_poweron);
+
+acpi_status acpihp_slot_poweroff(struct acpihp_slot *slot)
+{
+	if (slot == NULL) {
+		ACPIHP_DEBUG("invalid parameter.\n");
+		return AE_BAD_PARAMETER;
+	} else if (slot->slot_ops == NULL || slot->slot_ops->poweroff == NULL) {
+		ACPIHP_SLOT_DEBUG(slot, "operation not supported.\n");
+		return AE_SUPPORT;
+	}
+
+	return slot->slot_ops->poweroff(slot->handle);
+}
+EXPORT_SYMBOL_GPL(acpihp_slot_poweroff);
+
+/* SYSFS interfaces */
+static ssize_t acpihp_slot_object_show(struct device *d,
+		struct device_attribute *attr, char *buf)
+{
+	acpi_status rc;
+	ssize_t sz = -EINVAL;
+	struct acpihp_slot *slot = to_acpihp_slot(d);
+	struct acpi_buffer path = {ACPI_ALLOCATE_BUFFER, NULL};
+
+	rc = acpi_get_name(slot->handle, ACPI_FULL_PATHNAME, &path);
+	if (ACPI_SUCCESS(rc)) {
+		sz = snprintf(buf, PAGE_SIZE, "%s\n", (char *)path.pointer);
+		kfree(path.pointer);
+	}
+
+	return sz;
+}
+
+static ssize_t acpihp_slot_state_show(struct device *d,
+		struct device_attribute *attr, char *buf)
+{
+	enum acpihp_slot_state state;
+	acpi_status status;
+	unsigned long long sta;
+	struct acpihp_slot *slot = to_acpihp_slot(d);
+
+	state = slot->state < 0 || slot->state >= ACPIHP_SLOT_STATE_MAX ?
+		ACPIHP_SLOT_STATE_UNKNOWN : slot->state;
+
+	/*
+	 * There's no standard ACPI interfaces to notify the hotplug driver
+	 * when device presence changes, so check it for sure.
+	 */
+	if (ACPIHP_SLOT_STATE_ABSENT == state ||
+	    ACPIHP_SLOT_STATE_PRESENT == state) {
+		status = acpihp_slot_get_status(slot, &sta);
+		if (ACPI_SUCCESS(status)) {
+			if (sta & ACPI_STA_DEVICE_PRESENT)
+				state = ACPIHP_SLOT_STATE_PRESENT;
+			else
+				state = ACPIHP_SLOT_STATE_ABSENT;
+		}
+	}
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", acpihp_slot_states[state]);
+}
+
+static ssize_t acpihp_slot_status_show(struct device *d,
+		struct device_attribute *attr, char *buf)
+{
+	struct acpihp_slot *slot = to_acpihp_slot(d);
+	u32 status = slot->flags & ACPIHP_SLOT_STATUS_MASK;
+
+	return snprintf(buf, PAGE_SIZE, "%s\n", acpihp_slot_status[status]);
+}
+
+static ssize_t acpihp_slot_capabilities_show(struct device *d,
+		struct device_attribute *attr, char *buf)
+{
+	ssize_t sz;
+	struct acpihp_slot *slot = to_acpihp_slot(d);
+	u32 cap = slot->capabilities;
+
+	sz = snprintf(buf, PAGE_SIZE, "%s%s%s%s%s%s",
+		(cap & ACPIHP_SLOT_CAP_ONLINE) ? "online," : "",
+		(cap & ACPIHP_SLOT_CAP_OFFLINE) ? "offline," : "",
+		(cap & ACPIHP_SLOT_CAP_POWERON) ? "poweron," : "",
+		(cap & ACPIHP_SLOT_CAP_POWEROFF) ? "poweroff," : "",
+		(cap & ACPIHP_SLOT_CAP_HOTPLUG) ? "hotplug," : "",
+		(cap & ACPIHP_SLOT_CAP_MIGRATE) ? "migrate," : "");
+
+	/* Change the last ',' to '\n' */
+	BUG_ON(sz == 0);
+	if (sz)
+		buf[sz - 1] = '\n';
+
+	return sz;
+}
+
+struct device_attribute acpihp_slot_dev_attrs[] = {
+	__ATTR(object, S_IRUGO, acpihp_slot_object_show, NULL),
+	__ATTR(state, S_IRUGO, acpihp_slot_state_show, NULL),
+	__ATTR(status, S_IRUGO, acpihp_slot_status_show, NULL),
+	__ATTR(capabilities, S_IRUGO, acpihp_slot_capabilities_show, NULL),
+	__ATTR_NULL
+};
+
+/* The device class to support ACPI hotplug slots. */
+struct class acpihp_slot_class = {
+	.name		= "acpihp",
+	.dev_release	= &acpihp_slot_release,
+	.dev_attrs	= acpihp_slot_dev_attrs,
+};
+EXPORT_SYMBOL_GPL(acpihp_slot_class);
+
+/* Initialize the ACPI based system device hotplug core logic */
+int acpihp_core_init(void)
+{
+	int retval = 0;
+	struct kset *acpi_bus_kset;
+
+	mutex_lock(&acpihp_mutex);
+	BUG_ON(acpihp_class_count < 0);
+
+	if (acpihp_class_count == 0) {
+		/* create directory /sys/bus/acpi/slots */
+		acpi_bus_kset = bus_get_kset(&acpi_bus_type);
+		acpihp_slot_kset = kset_create_and_add("slots", NULL,
+						       &acpi_bus_kset->kobj);
+		if (!acpihp_slot_kset) {
+			ACPIHP_DEBUG("fails to create kset.\n");
+			retval = -ENOMEM;
+			goto out_unlock;
+		}
+
+		retval = class_register(&acpihp_slot_class);
+		if (retval) {
+			ACPIHP_DEBUG("fails to register acpihp_slot_class.\n");
+			kset_unregister(acpihp_slot_kset);
+			goto out_unlock;
+		}
+	}
+
+	acpihp_class_count++;
+out_unlock:
+	mutex_unlock(&acpihp_mutex);
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(acpihp_core_init);
+
+/* Deinitialize the ACPI based system device hotplug core logic */
+void acpihp_core_fini(void)
+{
+	mutex_lock(&acpihp_mutex);
+	BUG_ON(acpihp_class_count <= 0);
+	--acpihp_class_count;
+	if (acpihp_class_count == 0) {
+		class_unregister(&acpihp_slot_class);
+		kset_unregister(acpihp_slot_kset);
+		acpihp_slot_kset = NULL;
+	}
+	mutex_unlock(&acpihp_mutex);
+}
+EXPORT_SYMBOL_GPL(acpihp_core_fini);
+
+#ifdef	DEBUG
+int acpihp_debug = 1;
+#else
+int acpihp_debug;
+#endif
+EXPORT_SYMBOL_GPL(acpihp_debug);
+module_param_named(debug, acpihp_debug, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(debug, "Enable debug mode");
diff --git a/include/acpi/acpi_hotplug.h b/include/acpi/acpi_hotplug.h
new file mode 100644
index 0000000..298f679
--- /dev/null
+++ b/include/acpi/acpi_hotplug.h
@@ -0,0 +1,208 @@ 
+/*
+ * Copyright (C) 2012 Huawei Tech. Co., Ltd.
+ * Copyright (C) 2012 Jiang Liu <jiang.liu@huawei.com>
+ * Copyright (C) 2012 Gaohuai Han <hangaohuai@huawei.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#ifndef	__ACPI_HOTPLUG_H__
+#define	__ACPI_HOTPLUG_H__
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/klist.h>
+#include <acpi/acpi.h>
+#include <acpi/acpi_drivers.h>
+
+#ifdef	CONFIG_ACPI_HOTPLUG
+
+#define	ACPIHP_SLOT_NAME_MAX_SIZE		16
+
+/* Types of system devices supported by the ACPI hotplug framework. */
+enum acpihp_dev_type {
+	ACPIHP_DEV_TYPE_UNKNOWN = 0,	/* Unknown device type */
+	ACPIHP_DEV_TYPE_CONTAINER,	/* ACPI container device */
+	ACPIHP_DEV_TYPE_MEM,		/* Memory device */
+	ACPIHP_DEV_TYPE_CPU,		/* Logical CPU device */
+	ACPIHP_DEV_TYPE_HOST_BRIDGE,	/* PCI/PCIe host bridge */
+	ACPIHP_DEV_TYPE_MAX
+};
+
+/*
+ * ACPI hotplug slot is an abstraction of receptacles where a group of
+ * system devices could be attached, just like PCI slot in PCI hotplug.
+ */
+enum acpihp_slot_type {
+	ACPIHP_SLOT_TYPE_UNKNOWN = 0,	/* Unknown slot type */
+	ACPIHP_SLOT_TYPE_COMMON,	/* Generic hotplug slot */
+	ACPIHP_SLOT_TYPE_NODE,		/* Node hosts CPU, MEM & IO devices */
+	ACPIHP_SLOT_TYPE_SYSTEM_BOARD,	/* System board hosts CPU & MEM */
+	ACPIHP_SLOT_TYPE_CPU,		/* CPU board */
+	ACPIHP_SLOT_TYPE_MEM,		/* Memory board */
+	ACPIHP_SLOT_TYPE_IOX,		/* IO eXtension board */
+	ACPIHP_SLOT_TYPE_MAX
+};
+
+/*
+ * State machine for ACPI hotplug slot:
+ *                     (POWERON)      (CONNECT)      (CONFIGURE)
+ * [ABSENT] <-> [PRESENT] <-> [POWERED] <-> [CONNECTED] <-> [CONFIGURED]
+ *                     (POWEROFF)    (DISCONNECT)   (UNCONFIGURE)
+ *
+ * [ABSENT]: no devices attached to the slot
+ * [PRESENT]: devices attached to the slot but powered off
+ * [POWERED]: devices attached to the slot have been powered on
+ * [CONNECTED]: ACPI device objects have been created for devices attached
+ *              to the slot, and ACPI device drivers have been bound to the
+ *              ACPI device objects
+ * [CONFIGURED]: devices attached to the slot have been added into the
+ *               running system
+ */
+enum acpihp_slot_state {
+	ACPIHP_SLOT_STATE_UNKNOWN = 0,
+	ACPIHP_SLOT_STATE_ABSENT,	/* slot is empty. */
+	ACPIHP_SLOT_STATE_PRESENT,	/* slot is populated. */
+	ACPIHP_SLOT_STATE_POWERED,	/* attached devices are powered. */
+	ACPIHP_SLOT_STATE_CONNECTED,	/* ACPI device nodes created. */
+	ACPIHP_SLOT_STATE_CONFIGURED,	/* attached devices are configured. */
+	ACPIHP_SLOT_STATE_POWERING_ON,	/* powering devices on */
+	ACPIHP_SLOT_STATE_POWERING_OFF,	/* powering devices off */
+	ACPIHP_SLOT_STATE_CONNECTING,	/* creating ACPI device nodes */
+	ACPIHP_SLOT_STATE_DISCONNECTING,/* destroying ACPI device nodes */
+	ACPIHP_SLOT_STATE_CONFIGURING,	/* configuring devices */
+	ACPIHP_SLOT_STATE_UNCONFIGURING,/* unconfigure devices */
+	ACPIHP_SLOT_STATE_MAX
+};
+
+/* Devices attached to the slot can't be hot-removed. */
+#define	ACPIHP_SLOT_FLAG_IRREMOVABLE	0x1
+/* Devices attached to the slot have encountered serious problems. */
+#define	ACPIHP_SLOT_FLAG_FAULT		0x2
+#define	ACPIHP_SLOT_STATUS_MASK		0x3
+/* Internal flag: devices attached to the slot have been registered. */
+#define	ACPIHP_SLOT_FLAG_REGISTERED	0x80000000
+
+/* Capabilities of ACPI hotplug slot. */
+#define	ACPIHP_SLOT_CAP_ONLINE		0x1  /* Logical online */
+#define	ACPIHP_SLOT_CAP_OFFLINE		0x2  /* Logical offline */
+#define	ACPIHP_SLOT_CAP_POWERON		0x4  /* Physical power on */
+#define	ACPIHP_SLOT_CAP_POWEROFF	0x8  /* Physical power off */
+#define	ACPIHP_SLOT_CAP_HOTPLUG		0x10 /* Physical hotplug */
+#define	ACPIHP_SLOT_CAP_MIGRATE		0x20 /* Device migration */
+
+struct acpihp_slot;
+
+/*
+ * Callbacks provided by the platform dependent hotplug slot enumeration driver,
+ * which will be used by the platform independent ACPI hotplug framework to
+ * manage and control ACPI hotplug slots.
+ */
+struct acpihp_slot_ops {
+	struct module *owner;
+	char *desc;
+	acpi_status (*init)(void);
+	void (*fini)(void);					/* optional */
+	acpi_status (*check)(acpi_handle handle);
+	acpi_status (*create)(struct acpihp_slot *slot);
+	void (*destroy)(struct acpihp_slot *slot);		/* optional */
+	acpi_status (*poweron)(struct acpihp_slot *slot);	/* optional */
+	acpi_status (*poweroff)(struct acpihp_slot *slot);	/* optional */
+	acpi_status (*get_status)(struct acpihp_slot *slot,
+				  u64 *status);			/* optional */
+};
+
+/* Device structure for ACPI hotplug slots. */
+struct acpihp_slot {
+	struct device			dev;
+	acpi_handle			handle;
+	u32				capabilities;
+	u32				flags;
+	enum acpihp_slot_type		type;
+	enum acpihp_slot_state		state;
+	struct acpihp_slot		*parent;
+	struct acpihp_slot_ops		*slot_ops;
+	void				*slot_data;
+	struct mutex			slot_mutex;
+	struct list_head		slot_list;
+	struct list_head		drvdata_list;
+	struct klist			dev_lists[ACPIHP_DEV_TYPE_MAX];
+	char				name[ACPIHP_SLOT_NAME_MAX_SIZE];
+};
+
+/* Device class for ACPI hotplug slots */
+extern struct class acpihp_slot_class;
+
+/* Initialize the ACPI based system device hotplug core logic */
+extern int acpihp_core_init(void);
+
+/* Deinitialize the ACPI based system device hotplug core logic */
+extern void acpihp_core_fini(void);
+
+/* Utility routines */
+extern int acpihp_dev_get_type(acpi_handle handle, enum acpihp_dev_type *type);
+extern bool acpihp_dev_match_ids(struct acpi_device_info *infop, char **ids);
+extern char *acpihp_get_slot_type_name(enum acpihp_slot_type type);
+
+/* Mark/unmark an ACPI object as an ACPI hotplug slot. */
+extern acpi_status acpihp_mark_slot(acpi_handle handle,
+				    struct acpihp_slot *slot);
+extern acpi_status acpihp_unmark_slot(acpi_handle handle);
+
+/* Check whether the ACPI object is a hotplug slot. */
+extern bool acpihp_is_slot(acpi_handle handle);
+
+/* Interfaces to manage ACPI hotplug slots */
+extern struct acpihp_slot *acpihp_alloc_slot(acpi_handle handle, char *name);
+extern int acpihp_register_slot(struct acpihp_slot *slot);
+extern void acpihp_unregister_slot(struct acpihp_slot *slot);
+extern struct acpihp_slot *acpihp_slot_get(struct acpihp_slot *slot);
+extern void acpihp_slot_put(struct acpihp_slot *slot);
+extern struct acpihp_slot *acpihp_get_slot(acpi_handle handle);
+
+/* Platform dependent hotplug hooks */
+extern acpi_status acpihp_slot_get_status(struct acpihp_slot *slot,
+					  u64 *status);
+extern acpi_status acpihp_slot_poweron(struct acpihp_slot *slot);
+extern acpi_status acpihp_slot_poweroff(struct acpihp_slot *slot);
+
+extern int acpihp_debug;
+
+#define ACPIHP_WARN(fmt, ...) \
+	pr_warn("acpihp@%s: " fmt,  __func__, ##__VA_ARGS__)
+
+#define ACPIHP_DEBUG(fmt, ...) \
+	do { \
+		if (acpihp_debug & 0x01) \
+			pr_warn("acpihp@%s: " fmt,  __func__, ##__VA_ARGS__); \
+	} while (0)
+
+#define	ACPIHP_SLOT_DEBUG(slot, fmt, ...) \
+	do { \
+		if (acpihp_debug & 0x01) \
+			dev_warn(&(slot)->dev, fmt, ##__VA_ARGS__); \
+	} while (0)
+
+#define	ACPIHP_SLOT_WARN(slot, fmt, ...) \
+	dev_warn(&(slot)->dev, fmt, ##__VA_ARGS__)
+
+#endif	/* CONFIG_ACPI_HOTPLUG */
+
+#endif	/* __ACPI_HOTPLUG_H__ */