linux-kernel - Re: dma_mapping

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Message-ID: <20070627202839.GC4344@rhun.congress.lan>
Date:	Wed, 27 Jun 2007 16:28:39 -0400
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Andi Kleen <ak@...e.de>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jan Beulich <jbeulich@...ell.com>,
	Tony Luck <tony.luck@...el.com>
Subject: Re: dma_mapping_ops for i386

On Wed, Jun 27, 2007 at 05:26:50PM +0200, Andi Kleen wrote:

> See the recent "quiet down swiotlb warnings" thread which uncovered
> quite some corpses in Xen's current IO setup.
> 
> Xen apparently bounces for multi page IOs which get merged from block
> lists because the block layer doesn't know they are not really 
> continuous in machine memory.
> 
> Proper fix is to tell the block layer to not merge in the first
> place instead.
>
> And probably some similar mechanism for network drivers that limits
> MTUs.

Will that guarantee that block and net IOs will not straddle a page
boundary?

Cheers,
Muli
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