On 21/05/2016 01:40, Stefan Hajnoczi wrote:
> while (req) {
> qemu_put_sbyte(f, 1);
Could you just put an extra 32-bit queue id here if num_queues > 1? A
guest with num_queues > 1 cannot be started on pre-2.7 QEMU, so you can
change the migration format (if virtio were using vmstate, it would be a
VMSTATE_UINT32_TEST).
Thanks,
Paolo
> qemu_put_virtqueue_element(f, &req->elem);
> req = req->next;
> + s->num_rq++;
> }
> qemu_put_sbyte(f, 0);
> +
> + /* In order to distinguish virtio-blk subsections from the generic virtio
> + * device subsections that follow we emit a terminating byte. Old
> versions
> + * of QEMU don't expect the terminating byte so, for compatibility, only
> + * write it when virtio-blk subsections are needed.
> + */
> + if (virtio_blk_mq_rq_indices_needed(s)) {
> + uint32_t i;
> +
> + s->mq_rq_indices = g_new(uint32_t, s->num_rq);
> + req = s->rq;
> + for (i = 0; i < s->num_rq; i++) {
> + s->mq_rq_indices[i] = virtio_get_queue_index(req->vq);
> + req = req->next;
> + }
> +
> + vmstate_save_state(f, &virtio_blk_vmstate, s, NULL);
> + qemu_put_ubyte(f, ~QEMU_VM_SUBSECTION);
> +
> + g_free(s->mq_rq_indices);
> + s->mq_rq_indices = NULL;
