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virtio-blk: clarify that there is at least 1 virtqueue

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It is not possible to instantiate a virtio-blk device with 0 virtqueues.
The following check is located in ->realize():

  if (!conf->num_queues) {
      error_setg(errp, "num-queues property must be larger than 0");
      return;
  }

Later on we access s->vq_aio_context[0] under the assumption that there
is as least one virtqueue. Hanna Czenczek <hreitz@redhat.com> noted that
it would help to show that the array index is already valid.

Add an assertion to document that s->vq_aio_context[0] is always
safe...and catch future code changes that break this assumption.

Suggested-by: Hanna Czenczek <hreitz@redhat.com>
Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20240206190610.107963-3-stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2024-02-06 14:06:07 -05:00 committed by Kevin Wolf
parent 1f995a4782
commit 5fbcbd50fc
1 changed files with 1 additions and 0 deletions
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hw/block/virtio-blk.c
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@ -1824,6 +1824,7 @@ static int virtio_blk_start_ioeventfd(VirtIODevice *vdev)
* Try to change the AioContext so that block jobs and other operations can
* co-locate their activity in the same AioContext. If it fails, nevermind.
*/
assert(nvqs > 0); /* enforced during ->realize() */
r = blk_set_aio_context(s->conf.conf.blk, s->vq_aio_context[0],
&local_err);
if (r < 0) {