Re: [edk2-devel] [PATCH v1 2/2] UefiCpuPkg/BaseXApicX2ApicLib: Implements AMD extended cpu topology

["Abdul Lateef Attar via groups.io" <AbdulLateef.Attar=amd.com@groups.io>]

Thanks Gerd for providing the inputs.

I'll enhance the logic accordingly and submit the V2 patch.

Thanks

AbduL

On 16-01-2024 15:11, Gerd Hoffmann wrote:
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>
>
> On Tue, Jan 16, 2024 at 12:31:21PM +0530, Abdul Lateef Attar wrote:
>> From: Abdul Lateef Attar <AbdulLateef.Attar@amd.com>
>>
>> This patch adds support for AMD's new extended topology.
>> If processor supports CPUID 80000026 leaf then obtain
>> the topology information using new method.
>> +  /// Check if extended toplogy supported
>> +  AsmCpuid (CPUID_EXTENDED_FUNCTION, &MaxExtendedCpuIdIndex, NULL, NULL, NULL);
>> +  if (MaxExtendedCpuIdIndex < AMD_CPUID_EXTENDED_TOPOLOGY) {
>> +    GetProcessorLocationByApicId (InitialApicId, Package, Core, Thread);
>> +    return;
>> +  }
> Sure this is correct?
>
> On Intel processors checking MaxExtendedCpuIdIndex alone is not enough,
> see commit 170d4ce8e90a ("UefiCpuPkg/BaseXApicX2ApicLib: fix
> CPUID_V2_EXTENDED_TOPOLOGY detection")
>
> Especially in virtual machines it can happen that the vCPU supports
> extended cpuid leaf N but does not support N-1, so checking
> MaxExtendedCpuIdIndex alone looks rather fragile to me.
>
> take care,
>    Gerd
>


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