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Re: [PATCH] iommu/dma-iommu: properly respect configured address space size

From Joerg Roedel <joro@8bytes.org>
Newsgroups linux.kernel
Subject Re: [PATCH] iommu/dma-iommu: properly respect configured address space size
Date 2016-11-10 17:00 +0100
Message-ID <sBZVE-8ak-33@gated-at.bofh.it> (permalink)
References <sAS0a-3Aq-31@gated-at.bofh.it> <sAS0a-3Aq-29@gated-at.bofh.it> <sBd4C-lV-7@gated-at.bofh.it>
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On Tue, Nov 08, 2016 at 11:37:23AM +0000, Robin Murphy wrote:
> TBH I've been pondering ripping the size stuff out of dma-iommu, as it
> all stems from me originally failing to understand what dma_32bit_pfn is
> actually for.

The point of dma_32bit_pfn is to allocate dma-address below 4G by
default. This is a performance optimization so that even devices capable
of 64bit DMA are using SAC by default instead of DAC.

Since it is the goal to share a dma-iommu implemenation between
architectures, I would rather prefer not to rip this stuff out.


	Joerg

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Thread

[PATCH] iommu/dma-iommu: properly respect configured address space size Marek Szyprowski <m.szyprowski@samsung.com> - 2016-11-07 14:20 +0100
  Re: [PATCH] iommu/dma-iommu: properly respect configured address  space size Robin Murphy <robin.murphy@arm.com> - 2016-11-08 12:50 +0100
    Re: [PATCH] iommu/dma-iommu: properly respect configured address space  size Marek Szyprowski <m.szyprowski@samsung.com> - 2016-11-08 15:00 +0100
      Re: [PATCH] iommu/dma-iommu: properly respect configured address  space size Robin Murphy <robin.murphy@arm.com> - 2016-11-08 15:50 +0100
        Re: [PATCH] iommu/dma-iommu: properly respect configured address space  size Marek Szyprowski <m.szyprowski@samsung.com> - 2016-11-08 16:00 +0100
          Re: [PATCH] iommu/dma-iommu: properly respect configured address  space size Robin Murphy <robin.murphy@arm.com> - 2016-11-10 15:10 +0100
    Re: [PATCH] iommu/dma-iommu: properly respect configured address  space size Joerg Roedel <joro@8bytes.org> - 2016-11-10 17:00 +0100
      Re: [PATCH] iommu/dma-iommu: properly respect configured address  space size Robin Murphy <robin.murphy@arm.com> - 2016-11-10 17:20 +0100

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