vhost-user-blk: add an option to skip GET_VRING_BASE for force shutdown

If we have a server running disk requests that is for whatever reason
hanging or not able to process any more IO requests but still has some
in-flight requests previously issued by the guest OS, QEMU will still
try to drain the vring before shutting down even if it was explicitly
asked to do a "force shutdown" via SIGTERM or QMP quit. This is not
useful since the guest is no longer running at this point since it was
killed by QEMU earlier in the process. At this point, we don't care
about whatever in-flight IO it might have pending, we just want QEMU
to shut down.

Add an option called "skip-get-vring-base-on-force-shutdown" to allow
SIGTERM/QMP quit() to actually act like a "force shutdown" at least
for vhost-user-blk devices since those require the drain operation
to shut down gracefully unlike, for example, network devices.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Message-Id: <20250609212547.2859224-4-d-tatianin@yandex-team.ru>
Acked-by: Raphael Norwitz <raphael@enfabrica.net>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 10 insertions, 1 deletions

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 0eebbcd..c0cc5f6 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -210,6 +210,7 @@ static int vhost_user_blk_stop(VirtIODevice *vdev)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     int ret;
+    bool force_stop = false;
 
     if (!s->started_vu) {
         return 0;
@@ -220,7 +221,11 @@ static int vhost_user_blk_stop(VirtIODevice *vdev)
         return 0;
     }
 
-    ret = vhost_dev_stop(&s->dev, vdev, true);
+    force_stop = s->skip_get_vring_base_on_force_shutdown &&
+                 qemu_force_shutdown_requested();
+
+    ret = force_stop ? vhost_dev_force_stop(&s->dev, vdev, true) :
+                       vhost_dev_stop(&s->dev, vdev, true);
 
     if (k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false) < 0) {
         error_report("vhost guest notifier cleanup failed: %d", ret);
@@ -584,6 +589,8 @@ static const Property vhost_user_blk_properties[] = {
                       VIRTIO_BLK_F_DISCARD, true),
     DEFINE_PROP_BIT64("write-zeroes", VHostUserBlk, parent_obj.host_features,
                       VIRTIO_BLK_F_WRITE_ZEROES, true),
+    DEFINE_PROP_BOOL("skip-get-vring-base-on-force-shutdown", VHostUserBlk,
+                     skip_get_vring_base_on_force_shutdown, false),
 };
 
 static void vhost_user_blk_class_init(ObjectClass *klass, const void *data)
diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h
index ea085ee..a10f785 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -50,6 +50,8 @@ struct VHostUserBlk {
     bool connected;
     /* vhost_user_blk_start/vhost_user_blk_stop */
     bool started_vu;
+
+    bool skip_get_vring_base_on_force_shutdown;
 };
 
 #endif