netdev - Re: [PATCH v2 net-next] net: Implement fast csum_partial for x86

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Message-ID: <568DC4C4.2050908@stressinduktion.org>
Date:	Thu, 7 Jan 2016 02:52:04 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Tom Herbert <tom@...bertland.com>, davem@...emloft.net,
	netdev@...r.kernel.org
Cc:	kernel-team@...com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org
Subject: Re: [PATCH v2 net-next] net: Implement fast csum_partial for x86_64

Hi Tom,

On 05.01.2016 19:41, Tom Herbert wrote:
> --- /dev/null
> +++ b/arch/x86/lib/csum-partial_64.S
> @@ -0,0 +1,147 @@
> +/* Copyright 2016 Tom Herbert <tom@...bertland.com>
> + *
> + * Checksum partial calculation
> + *
> + * __wsum csum_partial(const void *buff, int len, __wsum sum)
> + *
> + * Computes the checksum of a memory block at buff, length len,
> + * and adds in "sum" (32-bit)
> + *
> + * Returns a 32-bit number suitable for feeding into itself
> + * or csum_tcpudp_magic
> + *
> + * Register usage:
> + *   %rdi: argument 1, buff
> + *   %rsi: argument 2, length
> + *   %rdx: argument 3, add in value

I think you forgot to carry-add-in the %rdx register.

The assembly code replaces do_csum but not csum_partial.

Bye,
Hannes

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