As of commit 38738f7dbb ("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 766aa2de0f ("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 38738f7dbb.
Fix it by using virtio_queue_aio_attach_host_notifier_no_poll() for the
event virtqueue.
Reported-by: Fiona Ebner <f.ebner@proxmox.com>
Fixes: 766aa2de0f
("virtio-scsi: implement BlockDevOps->drained_begin()")
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20240202153158.788922-2-hreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit c42c3833e0)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
feb2073c86