On Tue, Jan 16, 2024 at 12:31:21PM +0530, Abdul Lateef Attar wrote:
> From: Abdul Lateef Attar <abdullateef.at...@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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