From 2b2967163da2cc394a52516f2fc0907bae20c609 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@redhat.com>
Date: Sun, 6 Jun 2010 14:48:06 +0300
Subject: [PATCH] --- yaml --- r: 202389 b: refs/heads/master c:
 a9221dd5ec125fbec1702fae016c6d2ea1a9a3da h: refs/heads/master i:   202387:
 34f902b5a83734abec29a676a730c89633dd5d89 v: v3

---
 [refs]                   |  2 +-
 trunk/arch/x86/kvm/mmu.c | 28 +++++++++++++++++++++-------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 3cb91fd3d865..788e8410b25f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ce061867aa2877605cda96fa8ec7dff15f70a983
+refs/heads/master: a9221dd5ec125fbec1702fae016c6d2ea1a9a3da
diff --git a/trunk/arch/x86/kvm/mmu.c b/trunk/arch/x86/kvm/mmu.c
index fbdca08b8d8c..ba2efcf2b86e 100644
--- a/trunk/arch/x86/kvm/mmu.c
+++ b/trunk/arch/x86/kvm/mmu.c
@@ -288,6 +288,21 @@ static void __set_spte(u64 *sptep, u64 spte)
 #endif
 }
 
+static u64 __xchg_spte(u64 *sptep, u64 new_spte)
+{
+#ifdef CONFIG_X86_64
+	return xchg(sptep, new_spte);
+#else
+	u64 old_spte;
+
+	do {
+		old_spte = *sptep;
+	} while (cmpxchg64(sptep, old_spte, new_spte) != old_spte);
+
+	return old_spte;
+#endif
+}
+
 static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
 				  struct kmem_cache *base_cache, int min)
 {
@@ -653,18 +668,17 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
 static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)
 {
 	pfn_t pfn;
+	u64 old_spte;
 
-	if (!is_rmap_spte(*sptep)) {
-		__set_spte(sptep, new_spte);
+	old_spte = __xchg_spte(sptep, new_spte);
+	if (!is_rmap_spte(old_spte))
 		return;
-	}
-	pfn = spte_to_pfn(*sptep);
-	if (*sptep & shadow_accessed_mask)
+	pfn = spte_to_pfn(old_spte);
+	if (old_spte & shadow_accessed_mask)
 		kvm_set_pfn_accessed(pfn);
-	if (is_writable_pte(*sptep))
+	if (is_writable_pte(old_spte))
 		kvm_set_pfn_dirty(pfn);
 	rmap_remove(kvm, sptep);
-	__set_spte(sptep, new_spte);
 }
 
 static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)