Re: [PATCH net-next] virtio_net: Increase RSS max key size to match NETDEV_RSS_KEY_LEN

On Thu, 22 Jan 2026 14:45:27 +0530 Srujana Challa wrote:

Increase VIRTIO_NET_RSS_MAX_KEY_SIZE from 40 to 52 bytes to align with
the kernel's standard RSS key length defined by NETDEV_RSS_KEY_LEN.

I've been meaning to bump NETDEV_RSS_KEY_LEN to 128 or some such.
Most modern drivers can't use netdev_rss_key_fill() either because
core generates a tiny key. And the devices support hashing over two
layers of IPv6 for tunnels.

Willem, WDYT? Is there a reason to keep the core key small?
Or deprecate netdev_rss_key_fill()?

The virtio specification requires devices to support at least 40 bytes
for the RSS key size. However, devices may support larger key sizes
up to 52 bytes (as reported by the device's rss_max_key_size config
field). This change allows such devices to work properly.
Previously, devices reporting rss_max_key_size > 40 would fail with
an error during initialization.

The driver already handles variable key sizes dynamically through
vi->rss_key_size, so increasing the maximum limit is safe and
maintains backward compatibility with devices that support smaller
key sizes.

-#define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
+#define VIRTIO_NET_RSS_MAX_KEY_SIZE     52