[ Resending, again to the correct list. Apologies to everybody
  who got this twice. ]

Hi,

This series adds support for CPU hot-unplug with OVMF.

Please see this in conjunction with the QEMU secureboot hot-unplug v2
series posted here (now upstreamed):
  https://lore.kernel.org/qemu-devel/20201207140739.3829993-1-imammedo@redhat.com/

Patches 1 and 3,
  ("OvmfPkg/CpuHotplugSmm: refactor hotplug logic")
  ("OvmfPkg/CpuHotplugSmm: add Qemu Cpu Status helper")
are either refactors or add support functions.

Patch 2 and 9,
  ("OvmfPkg/CpuHotplugSmm: collect hot-unplug events")
  ("OvmfPkg/SmmControl2Dxe: negotiate hot-unplug")
handle the QEMU protocol logic for collection of hot-unplug events or
to handle the protocol negotiation.

Patches 4 and 5,
  ("UefiCpuPkg: add CPU ejection support")
  ("OvmfPkg/SmmCpuFeaturesLib: init CPU ejection state")
setup and init the PiSmmCpuDxeSmm CPU ejection state.

Patches 6, 7, and 8,
  ("OvmfPkg/CpuHotplugSmm: support CPU eject")
  ("OvmfPkg/CpuHotplugSmm: introduce UnplugCpus()")
  ("OvmfPkg/CpuHotplugSmm: add worker to do CPU ejection")
contain the core of the changes. The first one adds a NOP CPU ejection
handler, the second processing CPU ejection events and removing the
CPUs to be unplugged in a pen, and the third doing the actual eject.

Patch 10 ("MdePkg: use CpuPause() in CpuDeadLoop()") is unrelated to the
series and just adds a CpuPause() in the CpuDeadLoop((). 

Testing (with QEMU 5.2.50):
 - Stable with randomized CPU plug/unplug (guest maxcpus=1,8,128)
 - Synthetic tests with simultaneous multi CPU hot-unplug
 - Negotiation with/without CPU hotplug enabled

Also at:
  github.com/terminus/edk2/ hot-unplug-v3

Changelog:
 v3:
  - Use a saner PCD based interface to share state between PiSmmCpuDxeSmm
    and OvmfPkg/CpuHotplugSmm
  - Cleaner split of the hot-unplug code

 v2:
  - Do the ejection via SmmCpuFeaturesRendezvousExit()
  URL: https://patchew.org/EDK2/20210107195515.106158-1-ankur.a.arora@oracle.com/

 RFC:
  URL: https://patchew.org/EDK2/20201208053432.2690694-1-ankur.a.arora@oracle.com/


Please review.

Thanks
Ankur

Ankur Arora (10):
  OvmfPkg/CpuHotplugSmm: refactor hotplug logic
  OvmfPkg/CpuHotplugSmm: collect hot-unplug events
  OvmfPkg/CpuHotplugSmm: add Qemu Cpu Status helper
  UefiCpuPkg: add CPU ejection support
  OvmfPkg/SmmCpuFeaturesLib: init CPU ejection state
  OvmfPkg/CpuHotplugSmm: support CPU eject
  OvmfPkg/CpuHotplugSmm: introduce UnplugCpus()
  OvmfPkg/CpuHotplugSmm: add worker to do CPU ejection
  OvmfPkg/SmmControl2Dxe: negotiate hot-unplug
  MdePkg: use CpuPause() in CpuDeadLoop()


 MdePkg/Library/BaseLib/CpuDeadLoop.c               |   4 +-
 OvmfPkg/CpuHotplugSmm/CpuHotplug.c                 | 424 ++++++++++++++++-----
 OvmfPkg/CpuHotplugSmm/CpuHotplugSmm.inf            |   1 +
 OvmfPkg/CpuHotplugSmm/QemuCpuhp.c                  |  58 ++-
 OvmfPkg/CpuHotplugSmm/QemuCpuhp.h                  |   6 +
 OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h  |   2 +
 .../Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c  |  68 ++++
 .../SmmCpuFeaturesLib/SmmCpuFeaturesLib.inf        |   3 +
 OvmfPkg/SmmControl2Dxe/SmiFeatures.c               |  21 +-
 UefiCpuPkg/Include/CpuHotPlugData.h                |  21 +
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf       |   1 +
 UefiCpuPkg/UefiCpuPkg.dec                          |   5 +
 UefiCpuPkg/UefiCpuPkg.uni                          |   4 +
 13 files changed, 515 insertions(+), 103 deletions(-)

-- 
2.9.3



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