[PATCH 6/6] vhost-user: Have reset_status fall back to reset

[Hanna Czenczek <hreitz@redhat.com>]

The only user of vhost_user_reset_status() is vhost_dev_stop(), which
only uses it as a fall-back to stop the back-end if it does not support
SUSPEND.  However, vhost-user's implementation is a no-op unless the
back-end supports SET_STATUS.

vhost-vdpa's implementation instead just calls
vhost_vdpa_reset_device(), implying that it's OK to fully reset the
device if SET_STATUS is not supported.

To be fair, vhost_vdpa_reset_device() does nothing but to set the status
to zero.  However, that may well be because vhost-vdpa has no method
besides this to reset a device.  In contrast, vhost-user has
RESET_DEVICE and a RESET_OWNER, which can be used instead.

While it is not entirely clear from documentation or git logs, from
discussions and the order of vhost-user protocol features, it appears to
me as if RESET_OWNER originally had no real meaning for vhost-user, and
was thus used to signal a device reset to the back-end.  Then,
RESET_DEVICE was introduced, to have a well-defined dedicated reset
command.  Finally, vhost-user received full STATUS support, including
SET_STATUS, so setting the device status to 0 is now the preferred way
of resetting a device.  Still, RESET_DEVICE and RESET_OWNER should
remain valid as fall-backs.

Therefore, have vhost_user_reset_status() fall back to
vhost_user_reset_device() if the back-end has no STATUS support.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
---
 hw/virtio/vhost-user.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 4507de5a92..53a881ec2a 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2833,6 +2833,8 @@ static void vhost_user_reset_status(struct vhost_dev *dev)
     if (virtio_has_feature(dev->protocol_features,
                            VHOST_USER_PROTOCOL_F_STATUS)) {
         vhost_user_set_status(dev, 0);
+    } else {
+        vhost_user_reset_device(dev);
     }
 }
 
-- 
2.41.0