On Thu, May 20, 2021 at 03:13:05PM +0100, Stefan Hajnoczi wrote:

Possible drawbacks of this approach:

- Hardware virtio_blk implementations may find virtqueue_disable_cb()
  expensive since it requires DMA. If such devices become popular then
  the virtio_blk driver could use a similar approach to NVMe when
  VIRTIO_F_ACCESS_PLATFORM is detected in the future.

- If a blk_poll() thread is descheduled it not only hurts polling
  performance but also delays completion of non-REQ_HIPRI requests on
  that virtqueue since vq notifications are disabled.

Yes, I think this is a dangerous configuration.  What argument exists
again just using dedicated poll queues?