Am 24.01.24 um 18:38 schrieb Hanna Czenczek:
> As of commit 38738f7dbbda90fbc161757b7f4be35b52205552 ("virtio-scsi:
> don't waste CPU polling the event virtqueue"), we only attach an io_read
> notifier for the virtio-scsi event virtqueue instead, and no polling
> notifiers. During operation, the event virtqueue is typically
> non-empty, but none of the buffers are intended to be used immediately.
> Instead, they only get used when certain events occur. Therefore, it
> makes no sense to continuously poll it when non-empty, because it is
> supposed to be and stay non-empty.
>
> We do this by using virtio_queue_aio_attach_host_notifier_no_poll()
> instead of virtio_queue_aio_attach_host_notifier() for the event
> virtqueue.
>
> Commit 766aa2de0f29b657148e04599320d771c36fd126 ("virtio-scsi: implement
> BlockDevOps->drained_begin()") however has virtio_scsi_drained_end() use
> virtio_queue_aio_attach_host_notifier() for all virtqueues, including
> the event virtqueue. This can lead to it being polled again, undoing
> the benefit of commit 38738f7dbbda90fbc161757b7f4be35b52205552.
>
> Fix it by using virtio_queue_aio_attach_host_notifier_no_poll() for the
> event virtqueue.
>
> Reported-by: Fiona Ebner <f.eb...@proxmox.com>
> Fixes: 766aa2de0f29b657148e04599320d771c36fd126
> ("virtio-scsi: implement BlockDevOps->drained_begin()")
> Signed-off-by: Hanna Czenczek <hre...@redhat.com>
Tested-by: Fiona Ebner <f.eb...@proxmox.com>
Reviewed-by: Fiona Ebner <f.eb...@proxmox.com>
