From: Felipe Franciosi <felipe@nutanix.com>
Date: Wed, 20 Sep 2017 18:53:06 +0000 (-0700)
Subject: virtio/vhost: reset dev->log after syncing
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=5c0ba1be37181bd8a7c96c7f81b19ae5f8e66e2d;p=qmiga%2Fqemu.git

virtio/vhost: reset dev->log after syncing

vhost_log_put() is called to decomission the dirty log between qemu and
a vhost device when stopping the device. Such a call can happen from
migration_completion().

Present code sets dev->log_size to zero too early in vhost_log_put(),
causing the sync check to always return false. As a consequence, the
last pass on the dirty bitmap never happens at the end of migration.

If a vhost device was busy (writing to guest memory) until the last
moments before vhost_virtqueue_stop(), this error will result in guest
memory corruption (at least) following migrations.

Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 5fd69f0b2e..ddc42f0f93 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -375,8 +375,6 @@ static void vhost_log_put(struct vhost_dev *dev, bool sync)
     if (!log) {
         return;
     }
-    dev->log = NULL;
-    dev->log_size = 0;
 
     --log->refcnt;
     if (log->refcnt == 0) {
@@ -396,6 +394,9 @@ static void vhost_log_put(struct vhost_dev *dev, bool sync)
 
         g_free(log);
     }
+
+    dev->log = NULL;
+    dev->log_size = 0;
 }
 
 static bool vhost_dev_log_is_shared(struct vhost_dev *dev)