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

[Paolo Bonzini <pbonzini@redhat.com>]

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.
> 
> https://bugzilla.tianocore.org/show_bug.cgi?id=216
> 
> 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 path
> 
>  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@redhat.com>

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

Paolo