vdpa: add vhost_vdpa->suspended parameter

This allows vhost_vdpa to track if it is safe to get the vring base from
the device or not.  If it is not, vhost can fall back to fetch idx from
the guest buffer again.

No functional change intended in this patch, later patches will use this
field.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230303172445.1089785-6-eperezma@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 1550b1e26a..517e3cdc8d 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1193,6 +1193,14 @@ static int vhost_vdpa_get_vring_base(struct vhost_dev *dev,
         return 0;
     }
 
+    if (!v->suspended) {
+        /*
+         * Cannot trust in value returned by device, let vhost recover used
+         * idx from guest.
+         */
+        return -1;
+    }
+
     ret = vhost_vdpa_call(dev, VHOST_GET_VRING_BASE, ring);
     trace_vhost_vdpa_get_vring_base(dev, ring->index, ring->num);
     return ret;