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Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory

From Dan Williams <dan.j.williams@intel.com>
Newsgroups linux.kernel
Subject Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory
Date 2017-04-19 01:00 +0200
Message-ID <txKgi-3qF-15@gated-at.bofh.it> (permalink)
References (6 earlier) <txIRb-2HH-5@gated-at.bofh.it> <txJ0S-2KJ-13@gated-at.bofh.it> <txJDz-3bW-1@gated-at.bofh.it> <txJNf-3f2-9@gated-at.bofh.it> <txK6B-3m1-1@gated-at.bofh.it>
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On Tue, Apr 18, 2017 at 3:42 PM, Jason Gunthorpe
<jgunthorpe@obsidianresearch.com> wrote:
> On Tue, Apr 18, 2017 at 03:28:17PM -0700, Dan Williams wrote:
>
>> Unlike the pci bus address offset case which I think is fundamental to
>> support since shipping archs do this toda
>
> But we can support this by modifying those arch's unique dma_ops
> directly.
>
> Eg as I explained, my p2p_same_segment_map_page() helper concept would
> do the offset adjustment for same-segement DMA.
>
> If PPC calls that in their IOMMU drivers then they will have proper
> support for this basic p2p, and the right framework to move on to more
> advanced cases of p2p.
>
> This really seems like much less trouble than trying to wrapper all
> the arch's dma ops, and doesn't have the wonky restrictions.

I don't think the root bus iommu drivers have any business knowing or
caring about dma happening between devices lower in the hierarchy.

>> I think it is ok to say p2p is restricted to a single sgl that gets
>> to talk to host memory or a single device.
>
> RDMA and GPU would be sad with this restriction...
>
>> That said, what's wrong with a p2p aware map_sg implementation
>> calling up to the host memory map_sg implementation on a per sgl
>> basis?
>
> Setting up the iommu is fairly expensive, so getting rid of the
> batching would kill performance..

When we're crossing device and host memory boundaries how much
batching is possible? As far as I can see you'll always be splitting
the sgl on these dma mapping boundaries.

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Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-16 17:50 +0200
  Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-16 18:50 +0200
    Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 00:40 +0200
      Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-17 07:20 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 09:30 +0200
          Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-17 19:00 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-17 19:10 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 07:30 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jerome Glisse <jglisse@redhat.com> - 2017-04-17 20:10 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 08:20 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 23:20 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 07:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-18 08:40 +0200
  Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-17 00:30 +0200
    Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 18:50 +0200
      Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 19:30 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 20:10 +0200
          Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 20:40 +0200
          Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 03:20 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 01:00 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 02:10 +0200
      Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 20:40 +0200
        Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 21:10 +0200
          Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 21:40 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 21:50 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 22:10 +0200
            Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 21:50 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jerome Glisse <jglisse@redhat.com> - 2017-04-18 22:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 22:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 22:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 03:20 +0200
              Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 23:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 23:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-18 23:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-18 23:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 00:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 00:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 00:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 01:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 01:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 03:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 00:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 01:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 01:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 01:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 03:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-18 23:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 00:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 01:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 04:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-04-19 03:30 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 18:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 18:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 19:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jerome Glisse <jglisse@redhat.com> - 2017-04-19 19:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 19:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 20:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 20:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 20:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-19 20:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 20:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-20 22:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory "Stephen  Bates" <sbates@raithlin.com> - 2017-04-21 01:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@intel.com> - 2017-04-21 07:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory "Stephen  Bates" <sbates@raithlin.com> - 2017-04-20 22:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 19:20 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 20:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 20:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 21:10 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 21:40 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-19 21:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2017-04-19 22:50 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-04-20 01:00 +0200
                Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Dan Williams <dan.j.williams@gmail.com> - 2017-04-20 02:10 +0200

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