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SubjectRe: [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags
Hi Joerg,

On Wed, Jul 26, 2017 at 6:15 PM, Joerg Roedel <> wrote:
> On Tue, Jul 04, 2017 at 10:55:55PM +0900, Tomasz Figa wrote:
>> Current implementation of __iommu_dma_alloc_pages() keeps adding
>> __GFP_HIGHMEM to GFP flags regardless of whether other zone flags are
>> already included in the incoming flags. If __GFP_DMA or __GFP_DMA32 is
>> set at the same time as __GFP_HIGHMEM, the allocation fails due to
>> invalid zone flag combination.
>> Fix this by checking for __GFP_DMA and __GFP_DMA32 in incoming GFP flags
>> and adding __GFP_HIGHMEM only if they are not present.
>> Signed-off-by: Tomasz Figa <>
> Isn't it better to mask out __GFP_DMA and __GFP_DMA32 in the allocation
> flags and only take them into account for iova allocation?
> When the IOMMU re-maps the DMA to this memory it doesn't matter where it
> is in system memory.

It's a platform specific knowledge and I'd say the generic helper is
not where it should be decided. Please see my reply to Robin for v1


Best regards.

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