[PATCH 5/6] vhost: mark dirty pages during map uninit

Jason Wang
2019-07-23T07:57:17Z

We don't mark dirty pages if the map was teared down outside MMU
notifier. This will lead untracked dirty pages. Fixing by marking
dirty pages during map uninit.

Reported-by: Michael S. Tsirkin <mst at redhat.com>
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual
address")
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vhost.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 89c9f08b5146..5b8821d00fe4 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -306,6 +306,18 @@ static void vhost_map_unprefetch(struct vhost_map *map)
 	kfree(map);
 }

+static void vhost_set_map_dirty(struct vhost_virtqueue *vq,
+				struct vhost_map *map, int index)
+{
+	struct vhost_uaddr *uaddr = &vq->uaddrs[index];
+	int i;
+
+	if (uaddr->write) {
+		for (i = 0; i < map->npages; i++)
+			set_page_dirty(map->pages[i]);
+	}
+}
+
 static void vhost_uninit_vq_maps(struct vhost_virtqueue *vq)
 {
 	struct vhost_map *map[VHOST_NUM_ADDRS];
@@ -315,8 +327,10 @@ static void vhost_uninit_vq_maps(struct vhost_virtqueue
*vq)
 	for (i = 0; i < VHOST_NUM_ADDRS; i++) {
 		map[i] = rcu_dereference_protected(vq->maps[i],
 				  lockdep_is_held(&vq->mmu_lock));
-		if (map[i])
+		if (map[i]) {
+			vhost_set_map_dirty(vq, map[i], i);
 			rcu_assign_pointer(vq->maps[i], NULL);
+		}
 	}
 	spin_unlock(&vq->mmu_lock);

@@ -354,7 +368,6 @@ static void vhost_invalidate_vq_start(struct vhost_virtqueue
*vq,
 {
 	struct vhost_uaddr *uaddr = &vq->uaddrs[index];
 	struct vhost_map *map;
-	int i;

 	if (!vhost_map_range_overlap(uaddr, start, end))
 		return;
@@ -365,10 +378,7 @@ static void vhost_invalidate_vq_start(struct
vhost_virtqueue *vq,
 	map = rcu_dereference_protected(vq->maps[index],
 					lockdep_is_held(&vq->mmu_lock));
 	if (map) {
-		if (uaddr->write) {
-			for (i = 0; i < map->npages; i++)
-				set_page_dirty(map->pages[i]);
-		}
+		vhost_set_map_dirty(vq, map, index);
 		rcu_assign_pointer(vq->maps[index], NULL);
 	}
 	spin_unlock(&vq->mmu_lock);
--
2.18.1