Date: Fri, 23 Oct 2009 00:00:57 +0900
To: dwmw2@infradead.org
Cc: alex.williamson@hp.com, iommu@lists.linux-foundation.org,
       linux-kernel@vger.kernel.org, mike.miller@hp.com
Subject: Re: [PATCH] intel-iommu: Fix alloc_coherent for pass-through
 devices
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
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	<1256222867.2990.47.camel@macbook.infradead.org>
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On Thu, 22 Oct 2009 23:47:47 +0900
David Woodhouse <dwmw2@infradead.org> wrote:

> On Thu, 2009-10-22 at 06:24 -0600, Alex Williamson wrote:
> > The coherent_dma_mask is independent of the dma_mask and can be set
> > separately by the device.  The default for any device that doesn't
> > specify one is 32bits.  iommu_should_identity_map() only checks the
> > dma_mask, not the coherent_dma_mask. 
> 
> Are you telling me that this particular device supports only a 32-bit
> coherent DMA mask, but that it _does_ support a 64-bit DMA mask for
> non-coherent DMA? On x86?

This is not related with architectures. This card support 64 bit
addresses but doesn't support 64 bit addresses for descriptors, etc.
There are several hardware that have such limit.
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