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Groups > linux.kernel > #1696909 > unrolled thread
| Started by | Joerg Roedel <joro@8bytes.org> |
|---|---|
| First post | 2017-07-26 11:20 +0200 |
| Last post | 2017-07-26 11:30 +0200 |
| Articles | 2 — 2 participants |
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Re: [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags Joerg Roedel <joro@8bytes.org> - 2017-07-26 11:20 +0200
Re: [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags Tomasz Figa <tfiga@chromium.org> - 2017-07-26 11:30 +0200
| From | Joerg Roedel <joro@8bytes.org> |
|---|---|
| Date | 2017-07-26 11:20 +0200 |
| Subject | Re: [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags |
| Message-ID | <u7qE1-6RT-7@gated-at.bofh.it> |
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 <tfiga@chromium.org> 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. Joerg
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| From | Tomasz Figa <tfiga@chromium.org> |
|---|---|
| Date | 2017-07-26 11:30 +0200 |
| Message-ID | <u7qNI-6Vf-9@gated-at.bofh.it> |
| In reply to | #1696909 |
Hi Joerg, On Wed, Jul 26, 2017 at 6:15 PM, Joerg Roedel <joro@8bytes.org> 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 <tfiga@chromium.org> > > 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 [1]. [1] https://patchwork.kernel.org/patch/9810921/ Best regards. Tomasz
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