[v2,6/6] KVM: MMU: using __xchg_spte more smarter

Commit Message

Xiao Guangrong July 16, 2010, 3:30 a.m. UTC

None

Patch

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fb3ae54..71e9268 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -682,9 +682,14 @@  static void rmap_remove(struct kvm *kvm, u64 *spte)
 static void set_spte_track_bits(u64 *sptep, u64 new_spte)
 {
 	pfn_t pfn;
-	u64 old_spte;
+	u64 old_spte = *sptep;
+
+	if (!shadow_accessed_mask || !is_shadow_present_pte(old_spte) ||
+	      old_spte & shadow_accessed_mask) {
+		__set_spte(sptep, new_spte);
+	} else
+		old_spte = __xchg_spte(sptep, new_spte);
 
-	old_spte = __xchg_spte(sptep, new_spte);
 	if (!is_rmap_spte(old_spte))
 		return;
 	pfn = spte_to_pfn(old_spte);