linux-kernel - Re: [PATCH] swiotlb: fix dma_alloc_coherent allocation failures with swiotlb

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Date:	Thu, 4 Sep 2008 09:44:41 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	andi@...stfloor.org, joerg.roedel@....com, mingo@...hat.com,
	tglx@...utronix.de, hpa@...or.com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org, kamezawa.hiroyu@...fujitsu.com,
	tony.luck@...el.com
Subject: Re: [PATCH] swiotlb: fix dma_alloc_coherent allocation failures with swiotlb

On Thu, Sep 04, 2008 at 01:11:47PM +0900, FUJITA Tomonori wrote:
> On Thu, 04 Sep 2008 00:09:51 +0200
> Andi Kleen <andi@...stfloor.org> wrote:
> 
> > Joerg Roedel <joerg.roedel@....com> writes:
> > 
> > > The SWIOTLB version of dma_alloc_coherent allocates all memory with
> > > GFP_DMA unconditionally. This leads sometimes unnecessary to allocation
> > > failures. This patch makes the allocation strategy to use the DMA32 zone
> > > first if this is possible. The changes are boot tested on AMD64 and
> > > compile tested for i386 and IA64.
> > 
> > The high level dma_alloc_coherent() does that anyways.
> 
> The high level dma_alloc_coherent means the tricks in
> arch/x86/pci-dma.c? If so, all the tricks has gone in tip/master.

Seems wrong -- that is something that is needed by multiple
IOMMUs. Pretty much all which work with real memory instead
of virtual mappings.

I also have an older swiotlb rewrite in the pipeline based on the DMA
allocator. The project got a little sidelined, but I hope to eventually 
forward port it again.

-Andi

-- 
ak@...ux.intel.com
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