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>

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1594ee0..5c4c166 100644 (file)
--- 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