> -----Original Message-----
> From: Ni, Ray [mailto:ray...@intel.com]
> Sent: Wednesday, February 26, 2020 2:57 AM
> To: Laszlo Ersek <ler...@redhat.com>; devel@edk2.groups.io; Duran, Leo
> <leo.du...@amd.com>; Wu, Hao A <hao.a...@intel.com>; Fu, Siyuan
> <siyuan...@intel.com>
> Cc: Dong, Eric <eric.d...@intel.com>
> Subject: RE: [edk2-devel] [PATCH 0/2] UefiCpuPkg/Library: Fix bug in
> MpInitLib
>
> Leo,
>
> > > BTW, reading the PlatformId MSR was already being done by
> > > MicrocodeDetect(), but it never affected AMD-based platforms as the
> > > flow never gets that far, since the Detect routine bails out early when it
> finds the size of the patch is zero.
>
> You are saying that PlatformId MSR access is not performed by CPU in old
> code because of the zero size uCode.
> But now with Hao or Siyuan's change, the PlatformId MSR access is always
> performed even when there is no uCode. It sounds like a regression to
> optimization to me.
> Did you evaluate the path to avoid accessing PlatformID MSR when uCode
> doesn't exist? So that the API to detect AMD processor is not needed at all.
[Duran, Leo]
Hi Ray,
I think your summary is pretty accurate, except that I'd say that avoiding a
READ from the PlatformId MSR
should happen solely based on the fact that the MSR simply does not exist on
AMD processors.
Then as a result of that, the usage of the PlatformId (as it relates to
microcode or anything else) must then be dealt with separately.
To that end, I think I covered all cases where the MSR is being read, and also
where PlatformId is being used.
(I also added comments for each case)
Thanks,
Leo.
>
> Thanks,
> Ray
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