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[34.86.60.15]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6dd32b2be9esm179389276d6.34.2025.01.09.06.13.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2025 06:13:34 -0800 (PST) Date: Thu, 09 Jan 2025 09:13:33 -0500 From: Willem de Bruijn To: Akihiko Odaki , Jonathan Corbet , Willem de Bruijn , Jason Wang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Michael S. Tsirkin" , Xuan Zhuo , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kselftest@vger.kernel.org, Yuri Benditovich , Andrew Melnychenko , Stephen Hemminger , gur.stavi@huawei.com, Akihiko Odaki Message-ID: <677fd98d89df1_362bc12942f@willemb.c.googlers.com.notmuch> In-Reply-To: <20250109-rss-v6-1-b1c90ad708f6@daynix.com> References: <20250109-rss-v6-0-b1c90ad708f6@daynix.com> <20250109-rss-v6-1-b1c90ad708f6@daynix.com> Subject: Re: [PATCH v6 1/6] virtio_net: Add functions for hashing Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Akihiko Odaki wrote: > They are useful to implement VIRTIO_NET_F_RSS and > VIRTIO_NET_F_HASH_REPORT. Toeplitz potentially has users beyond virtio. I wonder if we should from the start implement this as net/core/rss.c. > Signed-off-by: Akihiko Odaki > --- > include/linux/virtio_net.h | 188 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 188 insertions(+) > > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > index 02a9f4dc594d..3b25ca75710b 100644 > --- a/include/linux/virtio_net.h > +++ b/include/linux/virtio_net.h > @@ -9,6 +9,194 @@ > #include > #include > > +struct virtio_net_hash { > + u32 value; > + u16 report; > +}; > + > +struct virtio_net_toeplitz_state { > + u32 hash; > + const u32 *key; > +}; > + > +#define VIRTIO_NET_SUPPORTED_HASH_TYPES (VIRTIO_NET_RSS_HASH_TYPE_IPv4 | \ > + VIRTIO_NET_RSS_HASH_TYPE_TCPv4 | \ > + VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | \ > + VIRTIO_NET_RSS_HASH_TYPE_IPv6 | \ > + VIRTIO_NET_RSS_HASH_TYPE_TCPv6 | \ > + VIRTIO_NET_RSS_HASH_TYPE_UDPv6) > + > +#define VIRTIO_NET_RSS_MAX_KEY_SIZE 40 > + > +static inline void virtio_net_toeplitz_convert_key(u32 *input, size_t len) > +{ > + while (len >= sizeof(*input)) { > + *input = be32_to_cpu((__force __be32)*input); > + input++; > + len -= sizeof(*input); > + } > +} > + > +static inline void virtio_net_toeplitz_calc(struct virtio_net_toeplitz_state *state, > + const __be32 *input, size_t len) > +{ > + while (len >= sizeof(*input)) { > + for (u32 map = be32_to_cpu(*input); map; map &= (map - 1)) { > + u32 i = ffs(map); > + > + state->hash ^= state->key[0] << (32 - i) | > + (u32)((u64)state->key[1] >> i); > + } > + > + state->key++; > + input++; > + len -= sizeof(*input); > + } > +} Have you verified that this algorithm matches a known toeplitz implementation. And computes the expected values for the test inputs in https://learn.microsoft.com/en-us/windows-hardware/drivers/network/verifying-the-rss-hash-calculation We have a toeplitz implementation in tools/testing/selftests/net/toeplitz.c that can also be used as reference. > + > +static inline u8 virtio_net_hash_key_length(u32 types) > +{ > + size_t len = 0; > + > + if (types & VIRTIO_NET_HASH_REPORT_IPv4) > + len = max(len, > + sizeof(struct flow_dissector_key_ipv4_addrs)); > + > + if (types & > + (VIRTIO_NET_HASH_REPORT_TCPv4 | VIRTIO_NET_HASH_REPORT_UDPv4)) > + len = max(len, > + sizeof(struct flow_dissector_key_ipv4_addrs) + > + sizeof(struct flow_dissector_key_ports)); > + > + if (types & VIRTIO_NET_HASH_REPORT_IPv6) > + len = max(len, > + sizeof(struct flow_dissector_key_ipv6_addrs)); > + > + if (types & > + (VIRTIO_NET_HASH_REPORT_TCPv6 | VIRTIO_NET_HASH_REPORT_UDPv6)) > + len = max(len, > + sizeof(struct flow_dissector_key_ipv6_addrs) + > + sizeof(struct flow_dissector_key_ports)); > + > + return len + 4; Avoid magic constants. Please use sizeof or something else to signal what this 4 derives from.