From: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Date: Fri, 16 Jul 2010 03:27:10 +0000 (+0800)
Subject: KVM: MMU: don't atomicly set spte if it's not present
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=be233d49ea8c1fde9f4afec378dc2c2f16ab0263;p=linux-beck.git

KVM: MMU: don't atomicly set spte if it's not present

If the old mapping is not present, the spte.a is not lost, so no need
atomic operation to set it

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a04756a26fe2..9c7fae08291d 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -307,9 +307,10 @@ static void update_spte(u64 *sptep, u64 new_spte)
 {
 	u64 old_spte;
 
-	if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask)) {
+	if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
+	      !is_rmap_spte(*sptep))
 		__set_spte(sptep, new_spte);
-	} else {
+	else {
 		old_spte = __xchg_spte(sptep, new_spte);
 		if (old_spte & shadow_accessed_mask)
 			mark_page_accessed(pfn_to_page(spte_to_pfn(old_spte)));