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Fri, 10 Jan 2025 01:28:51 -0800 (PST) Message-ID: <0bcbbc09-e4dd-4e16-ac1a-c9d3f368c145@daynix.com> Date: Fri, 10 Jan 2025 18:28:46 +0900 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/6] virtio_net: Add functions for hashing To: Willem de Bruijn , Jonathan Corbet , 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 References: <20250109-rss-v6-0-b1c90ad708f6@daynix.com> <20250109-rss-v6-1-b1c90ad708f6@daynix.com> <677fd98d89df1_362bc12942f@willemb.c.googlers.com.notmuch> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <677fd98d89df1_362bc12942f@willemb.c.googlers.com.notmuch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/01/09 23:13, Willem de Bruijn wrote: > 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. Or in lib/toeplitz.c just as like lib/siphash.c. I just chose the easiest option to implement everything in include/linux/virtio_net.h. > > >> 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 Yes. > > 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.