virtio: support irqfd in virtio_notify_config()

virtio_error() calls virtio_notify_config() to inject a VIRTIO
Configuration Change Notification. This doesn't work from IOThreads
because the BQL is not held and the interrupt code path requires the
BQL.

Follow the same approach as virtio_notify() and use ->config_notifier
(an irqfd) when called from the IOThread.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250922220149.498967-4-stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
1 file changed