[Qemu-stable] [PULL 36/38] vhost: set the correct queue index in case of migration with multiqueue

[Michael S. Tsirkin]

From: Thibaut Collet <address@hidden>

When a live migration is started the log address to mark dirty pages is provided
to the vhost backend through the vhost_dev_set_log function.
This function is called for each queue pairs but the queue index is wrongly set:
always set to the first queue pair. Then vhost backend lost descriptor addresses
of the queue pairs greater than 1 and behaviour of the vhost backend is
unpredictable.

The queue index is computed by taking account of the vq_index (to retrieve the
queue pair index) and calling the vhost_get_vq_index method of the backend.

Signed-off-by: Thibaut Collet <address@hidden>
Cc: address@hidden
Acked-by: Michael S. Tsirkin <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Michael S. Tsirkin <address@hidden>
---
 hw/virtio/vhost.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index feeaaa4..de29968 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -656,13 +656,14 @@ static int vhost_dev_set_features(struct vhost_dev *dev, 
bool enable_log)
 
 static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
 {
-    int r, t, i;
+    int r, t, i, idx;
     r = vhost_dev_set_features(dev, enable_log);
     if (r < 0) {
         goto err_features;
     }
     for (i = 0; i < dev->nvqs; ++i) {
-        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
+        idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
+        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
                                      enable_log);
         if (r < 0) {
             goto err_vq;
@@ -671,7 +672,8 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool 
enable_log)
     return 0;
 err_vq:
     for (; i >= 0; --i) {
-        t = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
+        idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
+        t = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
                                      dev->log_enabled);
         assert(t >= 0);
     }
-- 
MST