linux-kernel - Re: [PATCH v2 2/5] x86: enable DMA CMA with swiotlb

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Date:	Fri, 17 Jan 2014 08:32:09 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Don Dutile <ddutile@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>,
	x86@...nel.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v2 2/5] x86: enable DMA CMA with swiotlb

2014/1/16 Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>:
> On Tue, Jan 14, 2014 at 11:13:47PM +0900, Akinobu Mita wrote:
>> The DMA Contiguous Memory Allocator support on x86 is disabled when
>> swiotlb config option is enabled.  So DMA CMA is always disabled on
>> x86_64 because swiotlb is always enabled.  This attempts to support
>> for DMA CMA with enabling swiotlb config option.
>>
>> The contiguous memory allocator on x86 is integrated in the function
>> dma_generic_alloc_coherent() which is .alloc callback in nommu_dma_ops
>> for dma_alloc_coherent().
>>
>> x86_swiotlb_alloc_coherent() which is .alloc callback in swiotlb_dma_ops
>> tries to allocate with dma_generic_alloc_coherent() firstly and then
>> swiotlb_alloc_coherent() is called as a fallback.
>>
>> The main part of supporting DMA CMA with swiotlb is that changing
>> x86_swiotlb_free_coherent() which is .free callback in swiotlb_dma_ops
>> for dma_free_coherent() so that it can distinguish memory allocated by
>> dma_generic_alloc_coherent() from one allocated by swiotlb_alloc_coherent()
>> and release it with dma_generic_free_coherent() which can handle contiguous
>> memory.  This change requires making is_swiotlb_buffer() global function.
>>
>> This also needs to change .free callback in the dma_map_ops for amd_gart
>> and sta2x11, because these dma_ops are also using
>> dma_generic_alloc_coherent().
>>
>> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>> Cc: David Woodhouse <dwmw2@...radead.org>
>> Cc: Don Dutile <ddutile@...hat.com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: Andi Kleen <andi@...stfloor.org>
>> Cc: x86@...nel.org
>> Cc: iommu@...ts.linux-foundation.org
>> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
>> Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> ---
>> No change from the previous version
>>
>>  arch/x86/Kconfig               | 2 +-
>>  arch/x86/include/asm/swiotlb.h | 7 +++++++
>>  arch/x86/kernel/amd_gart_64.c  | 2 +-
>>  arch/x86/kernel/pci-swiotlb.c  | 9 ++++++---
>>  arch/x86/pci/sta2x11-fixup.c   | 6 ++----
>>  include/linux/swiotlb.h        | 2 ++
>>  lib/swiotlb.c                  | 2 +-
>
> It looks reasonable from my perspective (as swiotlb maintainer).
>
> Not too thrilled about the  'is_swiotlb_buffer' but that code is
> quite small so it should be fast enough.

Thanks.  Can I get your Acked-by for this patch?
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