Re: [PATCH v2 4/8] checksum: add csum_iov()

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Feb 14, 2024 at 09:56:24AM +0100, Laurent Vivier wrote:
> Introduce the function csum_unfolded() that computes the unfolded
> 32-bit checksum of a data buffer, and call it from csum() that returns
> the folded value.
> 
> Introduce csum_iov() that computes the checksum using csum_folded() on
> all vectors of the iovec array and returns the folded result.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> 
> Notes:
>     v2:
>       - fix typo and superfluous space
>       - update comments
> 
>  checksum.c | 46 ++++++++++++++++++++++++++++++++++------------
>  checksum.h |  1 +
>  2 files changed, 35 insertions(+), 12 deletions(-)
> 
> diff --git a/checksum.c b/checksum.c
> index 65486b4625ba..ac2bc49f7eb0 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -385,16 +385,16 @@ less_than_128_bytes:
>  }
>  
>  /**
> - * csum() - Compute TCP/IP-style checksum
> - * @buf:	Input buffer
> - * @len:	Input length
> - * @init:	Initial 32-bit checksum, 0 for no pre-computed checksum
> + * csum_unfolded - Calculate the unfolded checksum of a data buffer.
>   *
> - * Return: 16-bit folded, complemented checksum
> + * @buf:   Input buffer
> + * @len:   Input length
> + * @init:  Initial 32-bit checksum, 0 for no pre-computed checksum
> + *
> + * Return: 32-bit unfolded, complemented checksum

This function neither folds nor complements (indeed, you can't
complement until after you fold).

>   */
> -/* NOLINTNEXTLINE(clang-diagnostic-unknown-attributes) */
>  __attribute__((optimize("-fno-strict-aliasing")))	/* See csum_16b() */
> -uint16_t csum(const void *buf, size_t len, uint32_t init)
> +uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init)
>  {
>  	intptr_t align = ROUND_UP((intptr_t)buf, sizeof(__m256i));
>  	unsigned int pad = align - (intptr_t)buf;
> @@ -408,16 +408,30 @@ uint16_t csum(const void *buf, size_t len, uint32_t init)
>  	if (len > pad)
>  		init = csum_avx2((void *)align, len - pad, init);
>  
> -	return (uint16_t)~csum_fold(init);
> +	return init;
>  }
> -
>  #else /* __AVX2__ */
> +/**
> + * csum_unfolded - Calculate the unfolded checksum of a data buffer.
> + *
> + * @buf:   Input buffer
> + * @len:   Input length
> + * @init:  Initial 32-bit checksum, 0 for no pre-computed checksum
> + *
> + * Return: 32-bit unfolded, complemented checksum
> + */
> +__attribute__((optimize("-fno-strict-aliasing")))	/* See csum_16b() */
> +uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init)
> +{
> +	return sum_16b(buf, len) + init;
> +}
> +#endif /* !__AVX2__ */
>  
>  /**
>   * csum() - Compute TCP/IP-style checksum
>   * @buf:	Input buffer
>   * @len:	Input length
> - * @sum:	Initial 32-bit checksum, 0 for no pre-computed checksum
> + * @init:	Initial 32-bit checksum, 0 for no pre-computed checksum
>   *
>   * Return: 16-bit folded, complemented checksum
>   */
> @@ -425,7 +439,15 @@ uint16_t csum(const void *buf, size_t len, uint32_t init)
>  __attribute__((optimize("-fno-strict-aliasing")))	/* See csum_16b() */
>  uint16_t csum(const void *buf, size_t len, uint32_t init)
>  {
> -	return (uint16_t)~csum_fold(sum_16b(buf, len) + init);
> +	return (uint16_t)~csum_fold(csum_unfolded(buf, len, init));
>  }
>  
> -#endif /* !__AVX2__ */


Function comment, please.

> +uint16_t csum_iov(struct iovec *iov, unsigned int n, uint32_t init)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < n; i++)
> +		init = csum_unfolded(iov[i].iov_base, iov[i].iov_len, init);
> +
> +	return (uint16_t)~csum_fold(init);
> +}
> diff --git a/checksum.h b/checksum.h
> index 21c0310d3804..6a20297a5826 100644
> --- a/checksum.h
> +++ b/checksum.h
> @@ -25,5 +25,6 @@ void csum_icmp6(struct icmp6hdr *icmp6hr,
>  		const struct in6_addr *saddr, const struct in6_addr *daddr,
>  		const void *payload, size_t len);
>  uint16_t csum(const void *buf, size_t len, uint32_t init);
> +uint16_t csum_iov(struct iovec *iov, unsigned int n, uint32_t init);
>  
>  #endif /* CHECKSUM_H */

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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