Re: NVMe vs DMA addressing limitations

From	Christoph Hellwig <hch@lst.de>
Newsgroups	linux.kernel
Subject	Re: NVMe vs DMA addressing limitations
Date	2017-01-12 14:20 +0100
Message-ID	<sYNsl-4qh-7@gated-at.bofh.it> (permalink)
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On Thu, Jan 12, 2017 at 12:56:07PM +0100, Arnd Bergmann wrote:
> That is an interesting question: We actually have the
> "DMA_ATTR_NO_KERNEL_MAPPING" for this case, and ARM implements
> it in the coherent interface, so that might be a good fit.

Yes. my WIP HMB patch uses DMA_ATTR_NO_KERNEL_MAPPING, although I'm
workin on x86 at the moment where it's a no-op.

> Implementing it in the streaming API makes no sense since we
> already have a kernel mapping here, but using a normal allocation
> (possibly with DMA_ATTR_NON_CONSISTENT or DMA_ATTR_SKIP_CPU_SYNC,
> need to check) might help on other architectures that have
> limited amounts of coherent memory and no CMA.

Though about that - but in the end DMA_ATTR_NO_KERNEL_MAPPING implies
those, so instead of using lots of flags in driver I'd rather fix
up more dma_ops implementations to take advantage of
DMA_ATTR_NO_KERNEL_MAPPING.

Thread

Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Will Deacon <will.deacon@arm.com> - 2017-01-03 19:50 +0100
  Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-03 20:10 +0100
    Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Grygorii Strashko <grygorii.strashko@ti.com> - 2017-01-03 21:20 +0100
      Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-03 21:40 +0100
  Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@arndb.de> - 2017-01-04 00:20 +0100
    Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-04 07:40 +0100
      Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@arndb.de> - 2017-01-04 14:30 +0100
        Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-04 15:40 +0100
          Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@arndb.de> - 2017-01-04 15:50 +0100
            Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-04 16:40 +0100
              Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@arndb.de> - 2017-01-06 12:20 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-06 14:50 +0100
                [PATCH] arm64: do not set dma masks that device connection can't handle Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-06 15:40 +0100
                [PATCH] arm64: do not set dma masks that device connection can't handle Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-06 16:00 +0100
                Re: [PATCH] arm64: do not set dma masks that device connection can't  handle Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2017-01-08 08:20 +0100
                Re: [PATCH] arm64: do not set dma masks that device connection can't  handle Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-09 08:00 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@linaro.org> - 2017-01-09 15:10 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit  DMA mask Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-09 21:40 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit         DMA mask Christoph Hellwig <hch@lst.de> - 2017-01-09 22:00 +0100
                NVMe vs DMA addressing limitations Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-10 07:50 +0100
                Re: NVMe vs DMA addressing limitations Christoph Hellwig <hch@lst.de> - 2017-01-10 08:10 +0100
                Re: NVMe vs DMA addressing limitations Nikita Yushchenko <nikita.yoush@cogentembedded.com> - 2017-01-10 08:40 +0100
                Re: NVMe vs DMA addressing limitations Arnd Bergmann <arnd@linaro.org> - 2017-01-10 12:10 +0100
                Re: NVMe vs DMA addressing limitations Christoph Hellwig <hch@lst.de> - 2017-01-10 15:50 +0100
                Re: NVMe vs DMA addressing limitations Arnd Bergmann <arnd@linaro.org> - 2017-01-10 16:10 +0100
                Re: NVMe vs DMA addressing limitations Sagi Grimberg <sagi@grimberg.me> - 2017-01-12 11:10 +0100
                Re: NVMe vs DMA addressing limitations Arnd Bergmann <arnd@linaro.org> - 2017-01-12 13:00 +0100
                Re: NVMe vs DMA addressing limitations Christoph Hellwig <hch@lst.de> - 2017-01-12 14:20 +0100
                Re: NVMe vs DMA addressing limitations Arnd Bergmann <arnd@linaro.org> - 2017-01-10 12:00 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@linaro.org> - 2017-01-10 11:50 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit         DMA mask Christoph Hellwig <hch@lst.de> - 2017-01-10 15:50 +0100
                Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask Arnd Bergmann <arnd@linaro.org> - 2017-01-10 16:10 +0100

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