[PATCH RFC v3 2/9] virtio_net: Add functions for hashing

From: gur.stavi
Date: Mon Sep 16 2024 - 03:13:32 EST


+
+static inline void virtio_net_toeplitz(struct virtio_net_toeplitz_state *state,
+ const __be32 *input, size_t len)

The function calculates a hash value but its name does not make it
clear. Consider adding a 'calc'.

+{
+ u32 key;
+
+ while (len) {
+ state->key++;
+ key = be32_to_cpu(*state->key);

You perform be32_to_cpu to support both CPU endianities.
If you will follow with an unconditional swab32, you could run the
following loop on a more natural 0 to 31 always referring to bit 0
and avoiding !!(key & bit):

key = swab32(be32_to_cpu(*state->key));
for (i = 0; i < 32; i++, key >>= 1) {
if (be32_to_cpu(*input) & 1)
state->hash ^= state->key_buffer;
state->key_buffer = (state->key_buffer << 1) | (key & 1);
}


+
+ for (u32 bit = BIT(31); bit; bit >>= 1) {
+ if (be32_to_cpu(*input) & bit)
+ state->hash ^= state->key_buffer;
+
+ state->key_buffer =
+ (state->key_buffer << 1) | !!(key & bit);
+ }
+
+ input++;
+ len--;
+ }
+}
+
+static inline u32 virtio_net_hash_report(u32 types,
+ struct flow_dissector_key_basic key)
+{
+ switch (key.n_proto) {
+ case htons(ETH_P_IP):

Other parts of the code use be_to_cpu and cpu_to_be, Why use legacy
htons here?

+ if (key.ip_proto == IPPROTO_TCP &&
+ (types & VIRTIO_NET_RSS_HASH_TYPE_TCPv4))
+ return VIRTIO_NET_HASH_REPORT_TCPv4;
+
+ if (key.ip_proto == IPPROTO_UDP &&
+ (types & VIRTIO_NET_RSS_HASH_TYPE_UDPv4))
+ return VIRTIO_NET_HASH_REPORT_UDPv4;
+
+ if (types & VIRTIO_NET_RSS_HASH_TYPE_IPv4)
+ return VIRTIO_NET_HASH_REPORT_IPv4;
+
+ return VIRTIO_NET_HASH_REPORT_NONE;
+
+ case htons(ETH_P_IPV6):
+ if (key.ip_proto == IPPROTO_TCP &&
+ (types & VIRTIO_NET_RSS_HASH_TYPE_TCPv6))
+ return VIRTIO_NET_HASH_REPORT_TCPv6;
+
+ if (key.ip_proto == IPPROTO_UDP &&
+ (types & VIRTIO_NET_RSS_HASH_TYPE_UDPv6))
+ return VIRTIO_NET_HASH_REPORT_UDPv6;
+
+ if (types & VIRTIO_NET_RSS_HASH_TYPE_IPv6)
+ return VIRTIO_NET_HASH_REPORT_IPv6;
+
+ return VIRTIO_NET_HASH_REPORT_NONE;
+
+ default:
+ return VIRTIO_NET_HASH_REPORT_NONE;
+ }
+}
#endif /* _LINUX_VIRTIO_NET_H */

--
2.46.0