On Fri, Feb 06, 2026 at 05:31:54PM +0530, Srujana Challa wrote:

quoted

Replace hardcoded RSS max key size limit with NETDEV_RSS_KEY_LEN to
align with kernel's standard RSS key length. Add validation for RSS
key size against spec minimum (40 bytes) and driver maximum. When
validation fails, gracefully disable RSS features and continue
initialization rather than failing completely.

Signed-off-by: Srujana Challa <schalla@marvell.com>

I'd CC stable on this actually. failing when device is more capable was a bad
idea.
can you add a Fixes: tag, too? Thanks!

Sure.

quoted

---
 drivers/net/virtio_net.c | 62
+++++++++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 26 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index

db88dcaefb20..1fa4197dffc3 100644

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -381,7 +381,8 @@ struct receive_queue {
 	struct xdp_buff **xsk_buffs;
 };

-#define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
+#define VIRTIO_NET_RSS_MAX_KEY_SIZE     NETDEV_RSS_KEY_LEN
+#define VIRTIO_NET_RSS_MIN_KEY_SIZE     40

 /* Control VQ buffers: protected by the rtnl lock */  struct

control_buf { @@ -6823,38 +6824,47 @@ static int virtnet_probe(struct
virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
 		vi->has_rss_hash_report = true;

-	if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS)) {
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
 		vi->has_rss = true;

-		vi->rss_indir_table_size =
-			virtio_cread16(vdev, offsetof(struct virtio_net_config,
-				rss_max_indirection_table_length));
-	}
-	vi->rss_hdr = devm_kzalloc(&vdev->dev, virtnet_rss_hdr_size(vi),

GFP_KERNEL);

quoted

-	if (!vi->rss_hdr) {
-		err = -ENOMEM;
-		goto free;
-	}
-
 	if (vi->has_rss || vi->has_rss_hash_report) {
 		vi->rss_key_size =
 			virtio_cread8(vdev, offsetof(struct virtio_net_config,

rss_max_key_size));

quoted

-		if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
-			dev_err(&vdev->dev, "rss_max_key_size=%u exceeds

the limit %u.\n",

quoted

-				vi->rss_key_size,

VIRTIO_NET_RSS_MAX_KEY_SIZE);

quoted

-			err = -EINVAL;
-			goto free;
-		}

-		vi->rss_hash_types_supported =
-		    virtio_cread32(vdev, offsetof(struct virtio_net_config,

supported_hash_types));

quoted

-		vi->rss_hash_types_supported &=
-				~(VIRTIO_NET_RSS_HASH_TYPE_IP_EX |
-				  VIRTIO_NET_RSS_HASH_TYPE_TCP_EX |
-				  VIRTIO_NET_RSS_HASH_TYPE_UDP_EX);
+		/* Spec requires at least 40 bytes */
+		if (vi->rss_key_size < VIRTIO_NET_RSS_MIN_KEY_SIZE) {
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u is less than spec

minimum %u, disabling RSS\n",

quoted

+				 vi->rss_key_size,

VIRTIO_NET_RSS_MIN_KEY_SIZE);

quoted

+			vi->has_rss = false;
+			vi->has_rss_hash_report = false;
+		} else if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u exceeds driver limit

%u, disabling RSS\n",

quoted

+				 vi->rss_key_size,

VIRTIO_NET_RSS_MAX_KEY_SIZE);

quoted

+			vi->has_rss = false;
+			vi->has_rss_hash_report = false;
+		} else {
+			vi->rss_indir_table_size =
+				virtio_cread16(vdev, offsetof(struct

virtio_net_config,

quoted

+

rss_max_indirection_table_length));

quoted

+			vi->rss_hash_types_supported =
+			    virtio_cread32(vdev, offsetof(struct

virtio_net_config,

quoted

+

supported_hash_types));

quoted

+			vi->rss_hash_types_supported &=
+

	~(VIRTIO_NET_RSS_HASH_TYPE_IP_EX |

quoted

+

VIRTIO_NET_RSS_HASH_TYPE_TCP_EX |

quoted

+

VIRTIO_NET_RSS_HASH_TYPE_UDP_EX);

quoted

+
+			dev->hw_features |= NETIF_F_RXHASH;
+			dev->xdp_metadata_ops =

&virtnet_xdp_metadata_ops;

quoted

+		}
+	}

-		dev->hw_features |= NETIF_F_RXHASH;
-		dev->xdp_metadata_ops = &virtnet_xdp_metadata_ops;
+	vi->rss_hdr = devm_kzalloc(&vdev->dev, virtnet_rss_hdr_size(vi),

GFP_KERNEL);

quoted

+	if (!vi->rss_hdr) {
+		err = -ENOMEM;
+		goto free;
 	}

I feel these checks belong in virtnet_validate. Then we can disable features e.g.
by clearing VIRTIO_NET_F_RSS and host will have some visibility that RSS can't
be used.

Sure, will move to virtnet_validate() and clear feature bits.
Thanks!

quoted

 	if (virtio_has_feature(vdev,

VIRTIO_NET_F_GUEST_UDP_TUNNEL_GSO) ||

quoted

--
2.25.1