Re: [PATCH v2 0/3] Put AP into safe hlt-loop code on S3 path

[Laszlo Ersek <lersek@redhat.com>]

On 11/11/16 06:45, 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.
> 
> v2:
>   1. Make stack alignment per Laszlo's comment.
>   2. Trim whitespace at end of end per Laszlo's comment.
>   3. Update year mark in file header.
>   4. Enhancement on InterlockedDecrement() per Paolo's comment.
> 
> Jeff Fan (3):
>   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: Decrease mNumberToFinish in AP safe code
> 
>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c             | 33 +++++++++++++-
>  UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmFuncsArch.c | 29 +++++++++++-
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h    | 15 +++++++
>  UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c  | 63 ++++++++++++++++++++++++++-
>  4 files changed, 136 insertions(+), 4 deletions(-)
> 

Applied this locally to master (ffd6b0b1b65e) for testing. I tested the
series with a suspend-resume loop -- not a busy loop, just manually. (So
there was always one second or so between adjacent steps.)

No crashes or emulation failures, but the "AP going lost" issue remains
present -- sometimes Linux cannot bring up one of the four VCPUs after
resume.

In the Ia32 case, this "AP lost" symptom surfaced after the 6th resume.

In the Ia32X64 case, I experienced the symptom after the 89th resume.

Thanks
Laszlo