[2/2] KVM: Prevent internal slots from being COWed

Commit Message

Avi Kivity June 21, 2010, 8:18 a.m. UTC

None

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 33156a3..d9a33e6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5633,6 +5633,11 @@  int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				int user_alloc)
 {
 	int npages = memslot->npages;
+	int map_flags = MAP_PRIVATE | MAP_ANONYMOUS;
+
+	/* Prevent internal slot pages from being moved by fork()/COW. */
+	if (memslot->id >= KVM_MEMORY_SLOTS)
+		map_flags = MAP_SHARED | MAP_ANONYMOUS;
 
 	/*To keep backward compatibility with older userspace,
 	 *x86 needs to hanlde !user_alloc case.