[PATCH v4 net] virtio-net: validate features during probe

[Jason Wang]

We currently trigger BUG when VIRTIO_NET_F_CTRL_VQ
is not set but one of features depending on it is.
That's not a friendly way to report errors to
hypervisors.
Let's check, and fail probe instead.

Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Cc: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
Changes from V1:
- Drop NETIF_F_*_UFO from checklist
Changes from V2:
- only check the features for ctrl vq (this fix the real bug)
- better error message and simplify API
Changes from V3:
- pass dbit directly and even better error message
- typo fix
---
 drivers/net/virtio_net.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec2a8b4..cc53ff1 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1673,6 +1673,40 @@ static const struct attribute_group virtio_net_mrg_rx_group = {
 };
 #endif
 
+static bool virtnet_fail_on_feature(struct virtio_device *vdev,
+				    unsigned int fbit,
+				    const char *fname, const char *dname)
+{
+	if (!virtio_has_feature(vdev, fbit))
+		return false;
+
+	dev_err(&vdev->dev, "advertise feature %s but not %s",
+		fname, dname);
+
+	return true;
+}
+
+#define VIRTNET_FAIL_ON(vdev, fbit, dbit)			\
+	virtnet_fail_on_feature(vdev, fbit, #fbit, dbit)
+
+static bool virtnet_validate_features(struct virtio_device *vdev)
+{
+	if (!virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ) &&
+	    (VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_RX,
+			     "VIRTIO_NET_F_CTRL_VQ") ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_VLAN,
+			     "VIRTIO_NET_F_CTRL_VQ") ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE,
+			     "VIRTIO_NET_F_CTRL_VQ") ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_MQ, "VIRTIO_NET_F_CTRL_VQ") ||
+	     VIRTNET_FAIL_ON(vdev, VIRTIO_NET_F_CTRL_MAC_ADDR,
+			     "VIRTIO_NET_F_CTRL_VQ"))) {
+		return false;
+	}
+
+	return true;
+}
+
 static int virtnet_probe(struct virtio_device *vdev)
 {
 	int i, err;
@@ -1680,6 +1714,9 @@ static int virtnet_probe(struct virtio_device *vdev)
 	struct virtnet_info *vi;
 	u16 max_queue_pairs;
 
+	if (!virtnet_validate_features(vdev))
+		return -EINVAL;
+
 	/* Find if host supports multiqueue virtio_net device */
 	err = virtio_cread_feature(vdev, VIRTIO_NET_F_MQ,
 				   struct virtio_net_config,
-- 
1.9.1

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