vhost_net: don't set backend for the uninitialized virtqueue

We used to set backend unconditionally, this won't work for some
guests (e.g windows driver) who may not initialize all virtqueues. For
kernel backend, this will fail since it may try to validate the rings
during setting backend.

Fixing this by simply skipping the backend set when we find desc is
not ready.

Reviewed-by: Michael S. Tsirkin<mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index be3cc883709d0a3c3aeb78a92639ca98b4748a80..a6b719035c8433906bad323d8ea7849f1cc184fe 100644 (file)
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -244,6 +244,11 @@ static int vhost_net_start_one(struct vhost_net *net,
         qemu_set_fd_handler(net->backend, NULL, NULL, NULL);
         file.fd = net->backend;
         for (file.index = 0; file.index < net->dev.nvqs; ++file.index) {
+            if (!virtio_queue_enabled(dev, net->dev.vq_index +
+                                      file.index)) {
+                /* Queue might not be ready for start */
+                continue;
+            }
             r = vhost_net_set_backend(&net->dev, &file);
             if (r < 0) {
                 r = -errno;
@@ -256,6 +261,11 @@ fail:
     file.fd = -1;
     if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
         while (file.index-- > 0) {
+            if (!virtio_queue_enabled(dev, net->dev.vq_index +
+                                      file.index)) {
+                /* Queue might not be ready for start */
+                continue;
+            }
             int r = vhost_net_set_backend(&net->dev, &file);
             assert(r >= 0);
         }

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 2626a895cbb04d517f9bd7f76bdfdd274cffeb33..28056a7ef73a76511001596db8dae29b009fdb5a 100644 (file)
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2318,6 +2318,11 @@ hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
     return vdev->vq[n].vring.desc;
 }
 
+bool virtio_queue_enabled(VirtIODevice *vdev, int n)
+{
+    return virtio_queue_get_desc_addr(vdev, n) != 0;
+}
+
 hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n)
 {
     return vdev->vq[n].vring.avail;

diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index ce9516236a4d05d3274c40ecfc535cbd0867d8ed..7140381e3a0ca01e1fa05c0bd00054972fc42e5d 100644 (file)
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -282,6 +282,7 @@ typedef struct VirtIORNGConf VirtIORNGConf;
                       VIRTIO_F_IOMMU_PLATFORM, false)
 
 hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n);
+bool virtio_queue_enabled(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_avail_addr(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);