[PATCH v4 5/7] vhost-vdpa: backend feature should set only once

[Si-Wei Liu]

The vhost_vdpa_one_time_request() branch in
vhost_vdpa_set_backend_cap() incorrectly sends down
ioctls on vhost_dev with non-zero index. This may
end up with multiple VHOST_SET_BACKEND_FEATURES
ioctl calls sent down on the vhost-vdpa fd that is
shared between all these vhost_dev's.

To fix it, send down ioctl only once via the first
vhost_dev with index 0. Toggle the polarity of the
vhost_vdpa_one_time_request() test should do the
trick.

Fixes: 4d191cfdc7de ("vhost-vdpa: classify one time request")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 8adf7c0..6e3dbd9 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -665,7 +665,7 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
 
     features &= f;
 
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_one_time_request(dev)) {
         r = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, &features);
         if (r) {
             return -EFAULT;
-- 
1.8.3.1