From a500db4b868fc8254be5e7cc7227169f1c3ae2c1 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Tue, 31 Jul 2007 19:57:47 +1000
Subject: [PATCH] --- yaml --- r: 68376 b: refs/heads/master c:
 39214915f50f6ac2350355f2db63910d968fa790 h: refs/heads/master v: v3

---
 [refs]                       |  2 +-
 trunk/drivers/kvm/kvm_main.c | 13 ++++++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index bceeba4ba972..39eda750aa47 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b114b0804df7131cb6764b948c1c530c834fa3c0
+refs/heads/master: 39214915f50f6ac2350355f2db63910d968fa790
diff --git a/trunk/drivers/kvm/kvm_main.c b/trunk/drivers/kvm/kvm_main.c
index bfb1b6de0584..5dee3024579d 100644
--- a/trunk/drivers/kvm/kvm_main.c
+++ b/trunk/drivers/kvm/kvm_main.c
@@ -803,11 +803,14 @@ static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 	if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n))
 		goto out;
 
-	mutex_lock(&kvm->lock);
-	kvm_mmu_slot_remove_write_access(kvm, log->slot);
-	kvm_flush_remote_tlbs(kvm);
-	memset(memslot->dirty_bitmap, 0, n);
-	mutex_unlock(&kvm->lock);
+	/* If nothing is dirty, don't bother messing with page tables. */
+	if (any) {
+		mutex_lock(&kvm->lock);
+		kvm_mmu_slot_remove_write_access(kvm, log->slot);
+		kvm_flush_remote_tlbs(kvm);
+		memset(memslot->dirty_bitmap, 0, n);
+		mutex_unlock(&kvm->lock);
+	}
 
 	r = 0;