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SubjectRe: [PATCH] x86: enable DMA CMA with swiotlb
From
2013/11/20 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>:
> On Wed, Nov 20, 2013 at 08:32:19AM +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@samsung.com>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: x86@kernel.org
>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>> ---
>> 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 +-
>
> Looks OK, but before this goes anywhere I need to run regression tests
> on IA64 and the other users of SWIOTLB.

Thanks a lot for your review.


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