netdev - Re: [PATCH 1/3] myri10ge: fix management of the firmware 4KB boundary crossing restriction

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Message-ID: <461D04E6.5020103@garzik.org>
Date:	Wed, 11 Apr 2007 11:55:18 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Brice Goglin <brice@...i.com>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH 1/3] myri10ge: fix management of the firmware 4KB boundary
 crossing restriction

Brice Goglin wrote:
> Simpler way of dealing with the firmware 4KB boundary crossing
> restriction for rx buffers.  This fixes a variety of memory
> corruption issues when using an "uncommon" MTU with a 16KB
> page size.
> 
> Signed-off-by: Brice Goglin <brice@...i.com>
> ---
>  drivers/net/myri10ge/myri10ge.c |   19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> Index: linux-rc/drivers/net/myri10ge/myri10ge.c
> ===================================================================
> --- linux-rc.orig/drivers/net/myri10ge/myri10ge.c	2007-04-06 09:05:17.000000000 +0200
> +++ linux-rc/drivers/net/myri10ge/myri10ge.c	2007-04-10 21:03:59.000000000 +0200
> @@ -900,19 +900,9 @@
>  	/* try to refill entire ring */
>  	while (rx->fill_cnt != (rx->cnt + rx->mask + 1)) {
>  		idx = rx->fill_cnt & rx->mask;
> -
> -		if ((bytes < MYRI10GE_ALLOC_SIZE / 2) &&
> -		    (rx->page_offset + bytes <= MYRI10GE_ALLOC_SIZE)) {
> +		if (rx->page_offset + bytes <= MYRI10GE_ALLOC_SIZE) {
>  			/* we can use part of previous page */
>  			get_page(rx->page);
> -#if MYRI10GE_ALLOC_SIZE > 4096
> -			/* Firmware cannot cross 4K boundary.. */
> -			if ((rx->page_offset >> 12) !=
> -			    ((rx->page_offset + bytes - 1) >> 12)) {
> -				rx->page_offset =
> -				    (rx->page_offset + bytes) & ~4095;
> -			}
> -#endif
>  		} else {
>  			/* we need a new page */
>  			page =
> @@ -941,6 +931,13 @@
>  
>  		/* start next packet on a cacheline boundary */
>  		rx->page_offset += SKB_DATA_ALIGN(bytes);
> +
> +#if MYRI10GE_ALLOC_SIZE > 4096
> +		/* don't cross a 4KB boundary */
> +		if ((rx->page_offset >> 12) !=
> +		    ((rx->page_offset + bytes - 1) >> 12))
> +			rx->page_offset = (rx->page_offset + 4096) & ~4095;
> +#endif
>  		rx->fill_cnt++;
>  
>  		/* copy 8 descriptors to the firmware at a time */
> 

applied 1-3


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