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Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA

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On Fri, 2015-10-02 at 14:04 -0700, Nishanth Aravamudan wrote:
> Right, I did start with your advice and tried that approach, but it
> turned out I was wrong about the actual issue at the time. The problem
> for NVMe isn't actually the starting address alignment (which it can
> handle not being aligned to the device's page size). It doesn't handle
> (addr + len % dev_page_size != 0). That is, it's really a length
> alignment issue.
> 
> It seems incredibly device specific to have a an API into the DMA code
> to request an end alignment -- no other device seems to have this
> issue/design. If you think that's better, I can fiddle with that
> instead.
> 
> Sorry, I should have called this out better as an alternative
> consideration.

Nah it's fine. Ok. Also adding the alignment requirement to the API
would have been a much more complex patch since it would have had to
be implemented for all archs.

I think your current solution is fine.

Cheers,
Ben.

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[PATCH 0/2] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 19:20 +0200
  [PATCH 1/2] powerpc/iommu: expose IOMMU page shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 19:20 +0200
    [PATCH 2/2] drivers/nvme: default to the IOMMU page size on Power Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 19:30 +0200
      Re: [PATCH 2/2] drivers/nvme: default to the IOMMU page size on Power Christoph Hellwig <hch@infradead.org> - 2015-10-02 19:30 +0200
        Re: [PATCH 2/2] drivers/nvme: default to the IOMMU page size on Power Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 19:50 +0200
          Re: [PATCH 2/2] drivers/nvme: default to the IOMMU page size on Power Christoph Hellwig <hch@infradead.org> - 2015-10-02 19:50 +0200
  [PATCH 2/5 v2] powerpc/dma-mapping: override dma_get_page_shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:20 +0200
    [PATCH 3/5 v2] powerpc/dma: implement per-platform dma_get_page_shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:20 +0200
      [PATCH 4/5 v2] pseries/iommu: implement DDW-aware dma_get_page_shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:30 +0200
        [PATCH 5/5 v2] drivers/nvme: default to the IOMMU page size Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:40 +0200
        Re: [PATCH 4/5 v2] pseries/iommu: implement DDW-aware  dma_get_page_shift kbuild test robot <lkp@intel.com> - 2015-10-02 22:40 +0200
  [PATCH 1/5 v2] dma-mapping: add generic dma_get_page_shift API Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:20 +0200
  [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 22:20 +0200
    Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-02 23:10 +0200
      Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-10-02 23:40 +0200
        Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-03 00:00 +0200
    Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-10-02 23:30 +0200
      Re: [PATCH 0/5 v2] Fix NVMe driver support on Power with 32-bit DMA Christoph Hellwig <hch@infradead.org> - 2015-10-03 10:30 +0200

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