KVM: x86/mmu: Comment FNAME(sync_page) to document TLB flushing logic

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 <[email protected]>
Reviewed-by: Jim Mattson <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

0 files changed, 0 insertions, 0 deletions