commit 604b38ac0369bd50fcbb33344aa5553c071009f7
author Andrea Arcangeli <andrea@qumranet.com> Fri Jul 25 16:32:03 2008 +0200
committer Avi Kivity <avi@qumranet.com> Tue Jul 29 12:33:50 2008 +0300
tree 149325ef8ddbeb607a19052bb807383a6aa7a549
parent a1708ce8a362c4999f1201237ae7b77c4d13af82

KVM: Allow browsing memslots with mmu_lock

This allows reading memslots with only the mmu_lock hold for mmu
notifiers that runs in atomic context and with mmu_lock held.

Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9870ce4..c7b01ef 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3974,16 +3974,23 @@
 	 */
 	if (!user_alloc) {
 		if (npages && !old.rmap) {
+			unsigned long userspace_addr;
+
 			down_write(&current->mm->mmap_sem);
-			memslot->userspace_addr = do_mmap(NULL, 0,
-						     npages * PAGE_SIZE,
-						     PROT_READ | PROT_WRITE,
-						     MAP_SHARED | MAP_ANONYMOUS,
-						     0);
+			userspace_addr = do_mmap(NULL, 0,
+						 npages * PAGE_SIZE,
+						 PROT_READ | PROT_WRITE,
+						 MAP_SHARED | MAP_ANONYMOUS,
+						 0);
 			up_write(&current->mm->mmap_sem);
 
-			if (IS_ERR((void *)memslot->userspace_addr))
-				return PTR_ERR((void *)memslot->userspace_addr);
+			if (IS_ERR((void *)userspace_addr))
+				return PTR_ERR((void *)userspace_addr);
+
+			/* set userspace_addr atomically for kvm_hva_to_rmapp */
+			spin_lock(&kvm->mmu_lock);
+			memslot->userspace_addr = userspace_addr;
+			spin_unlock(&kvm->mmu_lock);
 		} else {
 			if (!old.user_alloc && old.rmap) {
 				int ret;