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

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Message-ID: <20240916071253.462-1-gur.stavi@huawei.com>
Date: Mon, 16 Sep 2024 10:12:53 +0300
From: <gur.stavi@...wei.com>
To: <akihiko.odaki@...nix.com>
CC: <andrew@...nix.com>, <corbet@....net>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <jasowang@...hat.com>, <kuba@...nel.org>,
	<kvm@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
	<mst@...hat.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>,
	<shuah@...nel.org>, <virtualization@...ts.linux-foundation.org>,
	<willemdebruijn.kernel@...il.com>, <xuanzhuo@...ux.alibaba.com>,
	<yuri.benditovich@...nix.com>
Subject: [PATCH RFC v3 2/9] virtio_net: Add functions for hashing

+
+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