[PATCH] vdpa: fix emulated guest announce feature status handling

[Gautam Dawar]

Guest announce capability is emulated by qemu in the .avail_handler
shadow virtqueue operation. It updates the status to success in
`*s->status` but incorrectly fetches the command execution
status from local variable `status` later in call to iov_from_buf().
As `status` is initialized to VIRTIO_NET_ERR, it results in a
warning "Failed to ack link announce" in virtio_net driver's
virtnet_ack_link_announce() function after VM Live Migration.
Also, I noticed an invalid check in vhost_vdpa_net_handle_ctrl_avail()
that reports an error because status is not updated in call to
virtio_net_handle_ctrl_iov():

    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, &out, 1);
    if (status != VIRTIO_NET_OK) {
        error_report("Bad CVQ processing in model");
    }
Adding an optional OUT status parameter to virtio_net_handle_ctrl_iov()
would help resolving this issue and also send the correct status
value to the virtio-net driver.

Signed-off-by: Gautam Dawar <gautam.dawar@amd.com>
---
 hw/net/virtio-net.c            | 9 +++++++--
 include/hw/virtio/virtio-net.h | 3 ++-
 net/vhost-vdpa.c               | 3 +--
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3ae909041a..36a75592da 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1503,7 +1503,8 @@ static int virtio_net_handle_mq(VirtIONet *n, uint8_t cmd,
 size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
                                   const struct iovec *in_sg, unsigned in_num,
                                   const struct iovec *out_sg,
-                                  unsigned out_num)
+                                  unsigned out_num,
+                                 virtio_net_ctrl_ack *status_out)
 {
     VirtIONet *n = VIRTIO_NET(vdev);
     struct virtio_net_ctrl_hdr ctrl;
@@ -1514,6 +1515,8 @@ size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
     if (iov_size(in_sg, in_num) < sizeof(status) ||
         iov_size(out_sg, out_num) < sizeof(ctrl)) {
         virtio_error(vdev, "virtio-net ctrl missing headers");
+       if (status_out)
+               *status_out = status;
         return 0;
     }
 
@@ -1540,6 +1543,8 @@ size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
     assert(s == sizeof(status));
 
     g_free(iov2);
+    if (status_out)
+           *status_out = status;
     return sizeof(status);
 }
 
@@ -1555,7 +1560,7 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, 
VirtQueue *vq)
         }
 
         written = virtio_net_handle_ctrl_iov(vdev, elem->in_sg, elem->in_num,
-                                             elem->out_sg, elem->out_num);
+                                             elem->out_sg, elem->out_num, 
NULL);
         if (written > 0) {
             virtqueue_push(vq, elem, written);
             virtio_notify(vdev, vq);
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index ef234ffe7e..da76cc414d 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -224,7 +224,8 @@ struct VirtIONet {
 size_t virtio_net_handle_ctrl_iov(VirtIODevice *vdev,
                                   const struct iovec *in_sg, unsigned in_num,
                                   const struct iovec *out_sg,
-                                  unsigned out_num);
+                                  unsigned out_num,
+                                 virtio_net_ctrl_ack *status);
 void virtio_net_set_netclient_name(VirtIONet *n, const char *name,
                                    const char *type);
 
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index de5ed8ff22..c72b338633 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -638,8 +638,7 @@ static int 
vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
         return VIRTIO_NET_ERR;
     }
 
-    status = VIRTIO_NET_ERR;
-    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, &out, 1);
+    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, &out, 1, &status);
     if (status != VIRTIO_NET_OK) {
         error_report("Bad CVQ processing in model");
     }
-- 
2.30.1