vhost: set log when updating used flags or avail event

We need to log writes when updating used flags and avail event
fields.  Otherwise the guest may see a stale value after migration and
miss notifying the host.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9a108038fe527393f6ac2b04a2104916b1518290..46822c0d9f7f007896cd19540703dae8853c897d 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -629,19 +629,6 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
        return 0;
 }
 
-int vhost_init_used(struct vhost_virtqueue *vq)
-{
-       int r;
-       if (!vq->private_data)
-               return 0;
-
-       r = put_user(vq->used_flags, &vq->used->flags);
-       if (r)
-               return r;
-       vq->signalled_used_valid = false;
-       return get_user(vq->last_used_idx, &vq->used->idx);
-}
-
 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
 {
        struct file *eventfp, *filep = NULL,
@@ -1008,6 +995,57 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
        return 0;
 }
 
+static int vhost_update_used_flags(struct vhost_virtqueue *vq)
+{
+       void __user *used;
+       if (put_user(vq->used_flags, &vq->used->flags) < 0)
+               return -EFAULT;
+       if (unlikely(vq->log_used)) {
+               /* Make sure the flag is seen before log. */
+               smp_wmb();
+               /* Log used flag write. */
+               used = &vq->used->flags;
+               log_write(vq->log_base, vq->log_addr +
+                         (used - (void __user *)vq->used),
+                         sizeof vq->used->flags);
+               if (vq->log_ctx)
+                       eventfd_signal(vq->log_ctx, 1);
+       }
+       return 0;
+}
+
+static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
+{
+       if (put_user(vq->avail_idx, vhost_avail_event(vq)))
+               return -EFAULT;
+       if (unlikely(vq->log_used)) {
+               void __user *used;
+               /* Make sure the event is seen before log. */
+               smp_wmb();
+               /* Log avail event write */
+               used = vhost_avail_event(vq);
+               log_write(vq->log_base, vq->log_addr +
+                         (used - (void __user *)vq->used),
+                         sizeof *vhost_avail_event(vq));
+               if (vq->log_ctx)
+                       eventfd_signal(vq->log_ctx, 1);
+       }
+       return 0;
+}
+
+int vhost_init_used(struct vhost_virtqueue *vq)
+{
+       int r;
+       if (!vq->private_data)
+               return 0;
+
+       r = vhost_update_used_flags(vq);
+       if (r)
+               return r;
+       vq->signalled_used_valid = false;
+       return get_user(vq->last_used_idx, &vq->used->idx);
+}
+
 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
                          struct iovec iov[], int iov_size)
 {
@@ -1479,34 +1517,20 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
                return false;
        vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
-               r = put_user(vq->used_flags, &vq->used->flags);
+               r = vhost_update_used_flags(vq);
                if (r) {
                        vq_err(vq, "Failed to enable notification at %p: %d\n",
                               &vq->used->flags, r);
                        return false;
                }
        } else {
-               r = put_user(vq->avail_idx, vhost_avail_event(vq));
+               r = vhost_update_avail_event(vq, vq->avail_idx);
                if (r) {
                        vq_err(vq, "Failed to update avail event index at %p: %d\n",
                               vhost_avail_event(vq), r);
                        return false;
                }
        }
-       if (unlikely(vq->log_used)) {
-               void __user *used;
-               /* Make sure data is seen before log. */
-               smp_wmb();
-               used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
-                       &vq->used->flags : vhost_avail_event(vq);
-               /* Log used flags or event index entry write. Both are 16 bit
-                * fields. */
-               log_write(vq->log_base, vq->log_addr +
-                          (used - (void __user *)vq->used),
-                         sizeof(u16));
-               if (vq->log_ctx)
-                       eventfd_signal(vq->log_ctx, 1);
-       }
        /* They could have slipped one in as we were doing that: make
         * sure it's written, then check again. */
        smp_mb();
@@ -1529,7 +1553,7 @@ void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
                return;
        vq->used_flags |= VRING_USED_F_NO_NOTIFY;
        if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
-               r = put_user(vq->used_flags, &vq->used->flags);
+               r = vhost_update_used_flags(vq);
                if (r)
                        vq_err(vq, "Failed to enable notification at %p: %d\n",
                               &vq->used->flags, r);