Re: [PATCH v3 0/4] x86/cpu/topology: Work around the nuances of virtualization on AMD/Hygon

[Borislav Petkov]

On Tue, Aug 19, 2025 at 07:58:52PM +0530, K Prateek Nayak wrote:
> This is possible, however what should be the right thing for
> CPUID_Fn8000001E_EBX [Core Identifiers] (Core::X86::Cpuid::CoreId)?
> 
> Should QEMU just wrap and start counting the Core Identifiers again
> from 0?
> 
> Or Should QEMU go ahead and populate just the
> CPUID_Fn8000001E_EAX [Extended APIC ID] (Core::X86::Cpuid::ExtApicId)
> fields and continue to zero out EBX and ECX when CoreID > 255?

I think the right thing to do is what the HW does (or will do), when it gets
to more than 256 APIC IDs - "cores" is ambiguous.

Perhaps something to discuss with hw folks internally first and then stick to
that plan everywhere, qemu included.

-- 
Regards/Gruss,
    Boris.

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