linux-kernel - Re: [PATCH 4/4] Bug Fix drivers/pci/intel-iommu.c: convert pfn_lo to VTD page address when calling iommu_flush_dev

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Date:	Wed, 05 Aug 2009 09:19:59 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Tony Luck <tony.luck@...el.com>, iommu@...ts.linux-foundation.org,
	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] Bug Fix drivers/pci/intel-iommu.c: convert pfn_lo
 to VTD page address when calling iommu_flush_dev_iotlb()

On Tue, 2009-08-04 at 15:11 -0700, Fenghua Yu wrote:
> The iova->pfn_lo should be converted to VTD page address before it's passed to
> iommu_flush_dev_iotlb().
> 
> This issue may cause DMA failure on PAGE_SIZE>VTD_PAGE_SIZE platforms e.g. ia64
> platforms.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>

I think this one is wrong. We allocate IOVA space in MM pages, not DMA
pages -- so the pfn_lo is an MM page already, and shifting by PAGE_SHIFT
is the right thing to do.

(I could be tempted to allocate it in DMA pages instead, but that's a
different story).

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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