linux-kernel - Re: [PATCH]: PCI: GART iommu alignment fixes [v2]

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Message-Id: <200807281523.35469.jbarnes@virtuousgeek.org>
Date:	Mon, 28 Jul 2008 15:23:35 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	joro@...tes.org, prarit@...hat.com, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH]: PCI: GART iommu alignment fixes [v2]

On Wednesday, July 23, 2008 4:14 pm FUJITA Tomonori wrote:
> On Thu, 24 Jul 2008 00:10:33 +0200
>
> Joerg Roedel <joro@...tes.org> wrote:
> > On Wed, Jul 23, 2008 at 07:19:43AM -0400, Prarit Bhargava wrote:
> > > pci_alloc_consistent/dma_alloc_coherent does not return size aligned
> > > addresses.
> > >
> > > >From Documentation/DMA-mapping.txt:
> > >
> > > "pci_alloc_consistent returns two values: the virtual address which you
> > > can use to access it from the CPU and dma_handle which you pass to the
> > > card.
> > >
> > > The cpu return address and the DMA bus master address are both
> > > guaranteed to be aligned to the smallest PAGE_SIZE order which
> > > is greater than or equal to the requested size.  This invariant
> > > exists (for example) to guarantee that if you allocate a chunk
> > > which is smaller than or equal to 64 kilobytes, the extent of the
> > > buffer you receive will not cross a 64K boundary."
> >
> > Interesting. Have you experienced any problems because of that
> > misbehavior in the GART code? AMD IOMMU currently also violates this
> > requirement. I will send a patch to fix that there too.
>
> IIRC, only PARISC and POWER IOMMUs follow the above rule. So I also
> wondered what problem he hit.

Prarit, what's the latest here?  The v3 patch I have from you doesn't apply to 
my tree but it looks like a good fix.  Care to send me a new patch against my 
for-linus branch?

Thanks,
Jesse
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