On 2024/09/16 10:01, gur.stavi@xxxxxxxxxx wrote:
+ +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); }Fixing myself, in previous version 'input' was tested against same bit. Advantage is less clear now, replacing !! with extra shift. However, since little endian CPUs are more common, the combination of swab32(be32_to_cpu(x) will actually become a nop. Similar tactic may be applied to 'input' by assigning it to local variable. This may produce more efficient version but not necessary easier to understand. key = bswap32(be32_to_cpu(*state->key)); for (u32 bit = BIT(31); bit; bit >>= 1, key >>= 1) { if (be32_to_cpu(*input) & bit) state->hash ^= state->key_buffer; state->key_buffer = (state->key_buffer << 1) | (key & 1); }
This unfortunately does not work. swab32() works at *byte*-level but we need to reverse the order of *bits*. bitrev32() is what we need, but it cannot eliminate be32_to_cpu().
Regards, Akihiko Odaki
