Re: [PATCH v8 15/20] KVM: x86: Guard valid XCR0.APX settings

[Jim Mattson]

On Wed, Sep 30, 2026 at 4:16 PM Chang S. Bae <chang.seok.bae@xxxxxxxxx> wrote:
>
> Prevent invalid XCR0.APX configurations in two cases: conflict with MPX
> and lack of SVM support.
>
> In the non-compacted XSAVE format, APX and MPX conflict on the same
> offset. Although MPX is being deprecated in practice, KVM should
> explicitly reject such configurations that set both bits.
>
> At this point, only VMX supports EGPRs. SVM will require corresponding
> extensions to handle EGPR indices.
>
> Updating the supported XCR0 mask will be done separately.
>
> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
> Link: https://lore.kernel.org/ab3f4937-38f5-4354-8850-bf773c159bbe@xxxxxxxxxx
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>