Re: [PATCH 03/43] KVM: SVM: Require exact CPUID.0x1 match when stuffing EDX at INIT

[Reiji Watanabe]

On Fri, Apr 23, 2021 at 5:47 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Do not allow an inexact CPUID "match" when querying the guest's CPUID.0x1
> to stuff EDX during INIT.  In the common case, where the guest CPU model
> is an AMD variant, allowing an inexact match is a nop since KVM doesn't
> emulate Intel's goofy "out-of-range" logic for AMD and Hygon.  If the
> vCPU model happens to be an Intel variant, an inexact match is possible
> if and only if the max CPUID leaf is precisely '0'. Aside from the fact
> that there's probably no CPU in existence with a single CPUID leaf, if
> the max CPUID leaf is '0', that means that CPUID.0.EAX is '0', and thus
> an inexact match for CPUID.0x1.EAX will also yield '0'.
>
> So, with lots of twisty logic, no functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Reiji Watanabe <reijiw@xxxxxxxxxx>