Re: [edk2-devel] [PATCH 0/2] UefiCpuPkg/Library: Fix bug in MpInitLib

["Laszlo Ersek" <lersek@redhat.com>]

On 02/26/20 17:39, Duran, Leo wrote:
> 
> 
>> -----Original Message-----
>> From: Laszlo Ersek [mailto:lersek@redhat.com]
>> Sent: Wednesday, February 26, 2020 11:21 AM
>> To: Duran, Leo <leo.duran@amd.com>; Ni, Ray <ray.ni@intel.com>;
>> devel@edk2.groups.io; Wu, Hao A <hao.a.wu@intel.com>; Fu, Siyuan
>> <siyuan.fu@intel.com>
>> Cc: Dong, Eric <eric.dong@intel.com>
>> Subject: Re: [edk2-devel] [PATCH 0/2] UefiCpuPkg/Library: Fix bug in
>> MpInitLib
>>
>> On 02/26/20 16:46, Duran, Leo wrote:
>>> BTW,
>>>
>>> I also considered adding a flag to CPU_MP_DATA to make the usage of
>> PlatformId a bit more explicit.
>>> E.g., something like CpuMpData-
>>> CpuData[ProcessorNumber].IsValidPlatformId... So the init code would look
>> like this:
>>>
>>>   //
>>>   // NOTE: PlatformId is not relevant on AMD platforms.
>>>   //
>>>   if (StandardSignatureIsAuthenticAMD ()) {
>>>     CpuMpData->CpuData[ProcessorNumber].IsValidPlatformId = FALSE;
>>>   else {
>>>     PlatformIdMsr.Uint64 = AsmReadMsr64 (MSR_IA32_PLATFORM_ID);
>>>     CpuMpData->CpuData[ProcessorNumber].PlatformId =
>> (UINT8)PlatformIdMsr.Bits.PlatformId;
>>>     CpuMpData->CpuData[ProcessorNumber].IsValidPlatformId = TRUE;
>>>   }
>>>
>>> This way "IsValidPlatformId" could be checked prior to using "PlatformId".
>>> Anyway, that seemed a bit overkill, so I opted against it... thoughts?
>>
>> I think a global flag is justified; in the above approach, "IsValidPlatformId"
>> would not vary across "ProcessorNumber", so it does look like useless
>> generality.
> [Duran, Leo] 
> Great point, Laszlo.
> Indeed, global makes senses in the case!
> I can prepare a v2-set to incorporate that.

No, sorry, that wasn't what I meant. I didn't try to suggest a global
variable. Instead, I meant that a "global check" (conceptually, i.e.
regardless of particular processor number) made sense.

I'm also not particularly *against* a global variable. In other words, I
didn't try to comment on using a global variable *at all*.

Using a global variable might as well work, I just feel that your
current patches are good enough.

Thanks
Laszlo