[Qemu-devel] [PATCH v2 1/1] vhost: set the correct queue index in case of migration with multiqueue

[Thibaut Collet]

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 provided to the
vhost_virtqueue_set_addr function 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 vhost_dev_set_log is modified to provide the correct queue index to the
vhost_virtqueue_set_addr function that calls internally the vhost_get_vq_index
to compute the expected vhost_vq_index for vhost kernel and vhost user.
This change implies a modification of the vhost_virtqueue_start function to
provide the index and not the vhost_vq_index.

Signed-off-by: Thibaut Collet <address@hidden>
---
 hw/virtio/vhost.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index feeaaa4..9311832 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -628,8 +628,9 @@ static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
                                     struct vhost_virtqueue *vq,
                                     unsigned idx, bool enable_log)
 {
+    int vhost_vq_index = dev->vhost_ops->vhost_get_vq_index(dev, idx);
     struct vhost_vring_addr addr = {
-        .index = idx,
+        .index = vhost_vq_index,
         .desc_user_addr = (uint64_t)(unsigned long)vq->desc,
         .avail_user_addr = (uint64_t)(unsigned long)vq->avail,
         .used_user_addr = (uint64_t)(unsigned long)vq->used,
@@ -662,7 +663,7 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool 
enable_log)
         goto err_features;
     }
     for (i = 0; i < dev->nvqs; ++i) {
-        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
+        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, dev->vq_index + i,
                                      enable_log);
         if (r < 0) {
             goto err_vq;
@@ -671,7 +672,7 @@ 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,
+        t = vhost_virtqueue_set_addr(dev, dev->vqs + i, dev->vq_index + i,
                                      dev->log_enabled);
         assert(t >= 0);
     }
@@ -836,7 +837,7 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
         goto fail_alloc_ring;
     }
 
-    r = vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_enabled);
+    r = vhost_virtqueue_set_addr(dev, vq, idx, dev->log_enabled);
     if (r < 0) {
         r = -errno;
         goto fail_alloc;
-- 
2.1.4