Re: [PATCH 2/2] KVM: x86/mmu: Comment FNAME(sync_page) to document TLB flushing logic

[Jim Mattson]

On Fri, May 13, 2022 at 12:50 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Add a comment to FNAME(sync_page) to explain why the TLB flushing logic
> conspiculously doesn't handle the scenario of guest protections being
> reduced.  Specifically, if synchronizing a SPTE drops execute protections,
> KVM will not emit a TLB flush, whereas dropping writable or clearing A/D
> bits does trigger a flush via mmu_spte_update().  Architecturally, until
> the GPTE is implicitly or explicitly flushed from the guest's perspective,
> KVM is not required to flush any old, stale translations.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>