Re: [PATCH 0/2] Put AP into safe hlt-loop code on S3 path

Fan, Jeff <>


I added patch #3 in v2 to do InterlockedDecrement (&mNumberToFinish) in the safe code.
This is very good comment to eliminate this gap.


-----Original Message-----
From: Paolo Bonzini [mailto:paolo.bonzini@...] On Behalf Of Paolo Bonzini
Sent: Thursday, November 10, 2016 5:59 PM
To: Fan, Jeff; edk2-devel@...
Subject: Re: [edk2] [PATCH 0/2] Put AP into safe hlt-loop code on S3 path

On 10/11/2016 07:07, Jeff Fan wrote:
On S3 path, we will wake up APs to restore CPU context in
PiSmmCpuDxeSmm driver. In case, one NMI or SMI happens, APs may exit
from hlt state and execute the instruction after HLT instruction.

But APs are not running on safe code, it leads OVMF S3 boot unstable.

I tested real platform with 64bit DXE.

Jeff Fan (2):
UefiCpuPkg/PiSmmCpuDxeSmm: Put AP into safe hlt-loop code on S3 path
UefiCpuPkg/PiSmmCpuDxeSmm: Place AP to 32bit protected mode on S3

UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 31 ++++++++++++++
UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmFuncsArch.c | 25 ++++++++++++
UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 13 ++++++
UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c | 59
4 files changed, 128 insertions(+)
Reviewed-by: Paolo Bonzini <pbonzini@...>

It would be slightly more robust to do the "InterlockedDecrement (&mNumberToFinish);" while in safe state, but the race window is really really small.


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