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

From Jerome Glisse <jglisse@redhat.com>
Newsgroups linux.kernel
Subject Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory
Date 2017-04-18 22:30 +0200
Message-ID <txHV8-29d-17@gated-at.bofh.it> (permalink)
References (2 earlier) <txEuf-8r4-43@gated-at.bofh.it> <txGcF-140-3@gated-at.bofh.it> <txGFI-1tx-11@gated-at.bofh.it> <txH8K-1CQ-1@gated-at.bofh.it> <txHiq-1Gh-21@gated-at.bofh.it>
Organization linux.* mail to news gateway

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> On Tue, Apr 18, 2017 at 12:35 PM, Logan Gunthorpe <logang@deltatee.com>
> wrote:
> >
> >
> > On 18/04/17 01:01 PM, Jason Gunthorpe wrote:
> >> Ultimately every dma_ops will need special code to support P2P with
> >> the special hardware that ops is controlling, so it makes some sense
> >> to start by pushing the check down there in the first place. This
> >> advice is partially motivated by how dma_map_sg is just a small
> >> wrapper around the function pointer call...
> >
> > Yes, I noticed this problem too and that makes sense. It just means
> > every dma_ops will probably need to be modified to either support p2p
> > pages or fail on them. Though, the only real difficulty there is that it
> > will be a lot of work.
> 
> I don't think you need to go touch all dma_ops, I think you can just
> arrange for devices that are going to do dma to get redirected to a
> p2p aware provider of operations that overrides the system default
> dma_ops. I.e. just touch get_dma_ops().

This would not work well for everyone, for instance on GPU we usualy
have buffer object with a mix of device memory and regular system
memory but call dma sg map once for the list.

Cheers,
Jérôme

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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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