[Qemu-devel] [PATCH v4 5/7] virtio-blk: live migrate s->rq with multiqueue

[Stefan Hajnoczi <stefanha@redhat.com>]

Add a field for the virtqueue index when migrating the s->rq request
list.  The new field is only needed when num_queues > 1.  Existing QEMUs
are unaffected by this change and therefore virtio-blk migration stays
compatible.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/virtio-blk.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 222611c..2ea8766 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -813,6 +813,11 @@ static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f)
 
     while (req) {
         qemu_put_sbyte(f, 1);
+
+        if (s->conf.num_queues > 1) {
+            qemu_put_be32(f, virtio_get_queue_index(req->vq));
+        }
+
         qemu_put_virtqueue_element(f, &req->elem);
         req = req->next;
     }
@@ -836,9 +841,22 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
     VirtIOBlock *s = VIRTIO_BLK(vdev);
 
     while (qemu_get_sbyte(f)) {
+        unsigned nvqs = s->conf.num_queues;
+        unsigned vq_idx = 0;
         VirtIOBlockReq *req;
+
+        if (nvqs > 1) {
+            vq_idx = qemu_get_be32(f);
+
+            if (vq_idx >= nvqs) {
+                error_report("Invalid virtqueue index in request list: %#x",
+                             vq_idx);
+                return -EINVAL;
+            }
+        }
+
         req = qemu_get_virtqueue_element(f, sizeof(VirtIOBlockReq));
-        virtio_blk_init_request(s, s->vq, req);
+        virtio_blk_init_request(s, virtio_get_queue(vdev, vq_idx), req);
         req->next = s->rq;
         s->rq = req;
     }
-- 
2.5.5