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As of commit38738f7dbb("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. Commit766aa2de0f("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 commit38738f7dbb. 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 commitc42c3833e0) Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>