KVM: MMU: Only mark_page_accessed() if the page was accessed by the guest

If the accessed bit is not set, the guest has never accessed this page
(at least through this spte), so there's no need to mark the page
accessed.  This provides more accurate data for the eviction algortithm.

Noted by Andrea Arcangeli.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1594ee06c92..5c4c16662c6 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -549,7 +549,8 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
                 return;
         sp = page_header(__pa(spte));
         page = spte_to_page(*spte);
-        mark_page_accessed(page);
+        if (*spte & PT_ACCESSED_MASK)
+                mark_page_accessed(page);
         if (is_writeble_pte(*spte))
                 kvm_release_page_dirty(page);
         else