virtio: sanity-check available index
Checking available index upon load instead of
only when vm is running makes is easier to
debug failures.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/virtio.c b/hw/virtio.c
index c8a0fc6..a2a657e 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -681,6 +681,7 @@
uint32_t features;
uint32_t supported_features =
vdev->binding->get_features(vdev->binding_opaque);
+ uint16_t num_heads;
if (vdev->binding->load_config) {
ret = vdev->binding->load_config(vdev->binding_opaque, f);
@@ -713,6 +714,16 @@
if (vdev->vq[i].pa) {
virtqueue_init(&vdev->vq[i]);
}
+ num_heads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
+ /* Check it isn't doing very strange things with descriptor numbers. */
+ if (num_heads > vdev->vq[i].vring.num) {
+ fprintf(stderr, "VQ %d size 0x%x Guest index 0x%x "
+ "inconsistent with Host index 0x%x: delta 0x%x\n",
+ i, vdev->vq[i].vring.num,
+ vring_avail_idx(&vdev->vq[i]),
+ vdev->vq[i].last_avail_idx, num_heads);
+ return -1;
+ }
if (vdev->binding->load_queue) {
ret = vdev->binding->load_queue(vdev->binding_opaque, i, f);
if (ret)
