On 10/31/23 11:43, Attar, AbdulLateef (Abdul Lateef) via groups.io wrote:
> [Public]
>
> Hi Laszlo and @Lin, Jacque
> Please find my response inline.
> Thanks
> AbduL
> -----Original Message-----
> From: Laszlo Ersek <ler...@redhat.com>
> Sent: Monday, October 30, 2023 7:34 PM
> To: devel@edk2.groups.io; Lin, Jacque <hsienchieh....@amd.com>
> Cc: Attar, AbdulLateef (Abdul Lateef) <abdullateef.at...@amd.com>; Chang,
> Abner <abner.ch...@amd.com>; Gerd Hoffmann <kra...@redhat.com>; Paolo Bonzini
> <pbonz...@redhat.com>
> Subject: Re: [edk2-devel] [PATCH] UefiCpuPkg/MmSaveStateLib: Remove checking
> Smm Rev ID in AMD MmSaveStateLib
> Are you saying that the
>
> SmmRevId < AMD_SMM_MIN_REV_ID_X64
>
> check will always evaluate to FALSE, and so the "return EFI_NOT_FOUND"
> branch is dead code?
> [Attar, AbdulLateef (Abdul Lateef)] that's right it always evaluate to FALSE
> If that's the case, then the patch seems right, but *why* is SmmRevId always
> greater than or equal to AMD_SMM_MIN_REV_ID_X64?
> [Attar, AbdulLateef (Abdul Lateef)] as per AMD64 Programmer's manual 10.2.4
> SMM-Revision Identifier.
> First 16bit contains the version, which 0x64 for 64bit architecture.
> Bit 16 and bit 17 always set 1.
> Hence SmmRevId is always equal to AMD_SMM_MIN_REV_ID_X64.
That may apply to physical hardware platforms, but does not apply to
QEMU/KVM, and this library instance is also used in OVMF (on QEMU/KVM),
since commit commit f2188fe5d155 ("OvmfPkg: Uses MmSaveStateLib
library", 2023-07-03).
Therefore, whatever you do in this library instance, must consider the
impact on OVMF on QEMU/KVM.
Thanks
Laszlo
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