linux-kernel - Re: [PATCH]iwlan dma mapping read and write changes

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Message-ID: <20090211185945.GQ27684@sequoia.sous-sol.org>
Date:	Wed, 11 Feb 2009 10:59:45 -0800
From:	Chris Wright <chrisw@...s-sol.org>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	David Woodhouse <dwmw2@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.sc.intel.com>,
	Johannes Berg <johannes@...solutions.net>,
	Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
	Tomas Winkler <tomas.winkler@...el.com>,
	Zhu Yi <yi.zhu@...el.com>, Chris Wright <chrisw@...s-sol.org>,
	LKML <linux-kernel@...r.kernel.org>,
	iommu@...ts.linux-foundation.org
Subject: Re: [PATCH]iwlan dma mapping read and write changes

* Fenghua Yu (fenghua.yu@...el.com) wrote:
> When iwlan runs on IOMMU, IOMMU generates a lot of PTE write faults because PTE
> write bit is not set on some of PTE's. This is because iwlan driver calls DMA
> mapping with PCI_DMA_TODEVICE which is read only in mapping PTE. But iwlan device
> actually writes to the mapped page to update its contents. This issue is not
> exposed in swiotlb. But VT-d hardware can capture this fault and stop the fault
> transaction.
> 
> The following patch fixes the issue.

Yes, plain old driver bug!  This fixes the iwlagn vt-d issue.


> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>

Tested-by: Chris Wright <chrisw@...s-sol.org>

thanks,
chris
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