[PATCH V2 net] virtio-net: validate features during probe

[Jason Wang]

This patch validates feature dependencies during probe and fail the probing
if a dependency is missed. This fixes the issues of hitting BUG()
when qemu fails to advertise features correctly. One example is booting
guest with ctrl_vq=off through qemu.

Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Cc: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
Changes from V1:
- Drop VIRTIO_NET_F_*_UFO from the checklist, since it was disabled
---
 drivers/net/virtio_net.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec2a8b4..b16a761 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1673,6 +1673,93 @@ static const struct attribute_group virtio_net_mrg_rx_group = {
 };
 #endif
 
+static int virtnet_validate_features(struct virtio_device *dev,
+				     unsigned int *table,
+				     int table_size,
+				     unsigned int feature)
+{
+	int i;
+
+	if (!virtio_has_feature(dev, feature)) {
+		for (i = 0; i < table_size; i++) {
+			unsigned int f = table[i];
+
+			if (virtio_has_feature(dev, f)) {
+				dev_err(&dev->dev,
+					"buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x was not",
+					f, feature);
+				return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int virtnet_check_features(struct virtio_device *dev)
+{
+	unsigned int features_for_ctrl_vq[] = {
+		VIRTIO_NET_F_CTRL_RX,
+		VIRTIO_NET_F_CTRL_VLAN,
+		VIRTIO_NET_F_GUEST_ANNOUNCE,
+		VIRTIO_NET_F_MQ,
+		VIRTIO_NET_F_CTRL_MAC_ADDR
+	};
+	unsigned int features_for_guest_csum[] = {
+		VIRTIO_NET_F_GUEST_TSO4,
+		VIRTIO_NET_F_GUEST_TSO6,
+		VIRTIO_NET_F_GUEST_ECN,
+	};
+	unsigned int features_for_host_csum[] = {
+		VIRTIO_NET_F_HOST_TSO4,
+		VIRTIO_NET_F_HOST_TSO6,
+		VIRTIO_NET_F_HOST_ECN,
+	};
+	int err;
+
+	err = virtnet_validate_features(dev, features_for_ctrl_vq,
+					ARRAY_SIZE(features_for_ctrl_vq),
+					VIRTIO_NET_F_CTRL_VQ);
+	if (err)
+		return err;
+
+	err = virtnet_validate_features(dev, features_for_guest_csum,
+					ARRAY_SIZE(features_for_guest_csum),
+					VIRTIO_NET_F_GUEST_CSUM);
+	if (err)
+		return err;
+
+	err = virtnet_validate_features(dev, features_for_host_csum,
+					ARRAY_SIZE(features_for_host_csum),
+					VIRTIO_NET_F_CSUM);
+	if (err)
+		return err;
+
+	if (virtio_has_feature(dev, VIRTIO_NET_F_GUEST_ECN) &&
+	    (!virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO4) ||
+	     !virtio_has_feature(dev, VIRTIO_NET_F_GUEST_TSO6))) {
+		dev_err(&dev->dev,
+			"buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
+			VIRTIO_NET_F_GUEST_ECN,
+			VIRTIO_NET_F_GUEST_TSO4,
+			VIRTIO_NET_F_GUEST_TSO6);
+		return -EINVAL;
+	}
+
+	if (virtio_has_feature(dev, VIRTIO_NET_F_HOST_ECN) &&
+	    (!virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO4) ||
+	     !virtio_has_feature(dev, VIRTIO_NET_F_HOST_TSO6))) {
+		dev_err(&dev->dev,
+			"buggy hyperviser: feature 0x%x was advertised but its dependency 0x%x or 0x%x was not",
+			VIRTIO_NET_F_HOST_ECN,
+			VIRTIO_NET_F_HOST_TSO4,
+			VIRTIO_NET_F_HOST_TSO6);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int virtnet_probe(struct virtio_device *vdev)
 {
 	int i, err;
@@ -1680,6 +1767,10 @@ static int virtnet_probe(struct virtio_device *vdev)
 	struct virtnet_info *vi;
 	u16 max_queue_pairs;
 
+	err = virtnet_check_features(vdev);
+	if (err)
+		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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