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Re: Enabling peer to peer device transactions for PCIe devices

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On Mon, Dec 05, 2016 at 10:48:58AM -0800, Dan Williams wrote:
> On Mon, Dec 5, 2016 at 10:39 AM, Logan Gunthorpe <logang@deltatee.com> wrote:
> > On 05/12/16 11:08 AM, Dan Williams wrote:
> >>
> >> I've already recommended that iopmem not be a block device and instead
> >> be a device-dax instance. I also don't think it should claim the PCI
> >> ID, rather the driver that wants to map one of its bars this way can
> >> register the memory region with the device-dax core.
> >>
> >> I'm not sure there are enough device drivers that want to do this to
> >> have it be a generic /sys/.../resource_dmableX capability. It still
> >> seems to be an exotic one-off type of configuration.
> >
> >
> > Yes, this is essentially my thinking. Except I think the userspace interface
> > should really depend on the device itself. Device dax is a good  choice for
> > many and I agree the block device approach wouldn't be ideal.
> >
> > Specifically for NVME CMB: I think it would make a lot of sense to just hand
> > out these mappings with an mmap call on /dev/nvmeX. I expect CMB buffers
> > would be volatile and thus you wouldn't need to keep track of where in the
> > BAR the region came from. Thus, the mmap call would just be an allocator
> > from BAR memory. If device-dax were used, userspace would need to lookup
> > which device-dax instance corresponds to which nvme drive.
> 
> I'm not opposed to mapping /dev/nvmeX.  However, the lookup is trivial
> to accomplish in sysfs through /sys/dev/char to find the sysfs path
> of

But CMB sounds much more like the GPU case where there is a
specialized allocator handing out the BAR to consumers, so I'm not
sure a general purpose chardev makes a lot of sense?

Jason

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Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-25 20:40 +0100
  Re: Enabling peer to peer device transactions for PCIe devices Christian König <deathsimple@vodafone.de> - 2016-11-25 21:50 +0100
    Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-25 22:20 +0100
  Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-28 18:00 +0100
    Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-11-28 19:30 +0100
      Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-11-28 22:40 +0100
        Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-28 23:30 +0100
    Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-28 20:10 +0100
      Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-11-30 17:30 +0100
        Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-11-30 19:10 +0100
          Re: Enabling peer to peer device transactions for PCIe devices "Stephen Bates" <sbates@raithlin.com> - 2016-12-04 14:10 +0100
          Re: Enabling peer to peer device transactions for PCIe devices "Stephen Bates" <sbates@raithlin.com> - 2016-12-04 14:50 +0100
            Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-05 18:20 +0100
              Re: Enabling peer to peer device transactions for PCIe devices Dan Williams <dan.j.williams@intel.com> - 2016-12-05 18:50 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Dan Williams <dan.j.williams@intel.com> - 2016-12-05 19:10 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-12-05 19:40 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Dan Williams <dan.j.williams@intel.com> - 2016-12-05 19:50 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-05 20:20 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-12-05 20:30 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-05 20:50 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-12-05 21:00 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Christoph Hellwig <hch@infradead.org> - 2016-12-05 21:10 +0100
                Re: Enabling peer to peer device transactions for PCIe devices "Stephen Bates" <sbates@raithlin.com> - 2016-12-06 09:30 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-06 17:40 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-12-06 18:00 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-06 18:30 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Logan Gunthorpe <logang@deltatee.com> - 2016-12-06 22:50 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Dan Williams <dan.j.williams@intel.com> - 2016-12-06 23:10 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Christoph Hellwig <hch@infradead.org> - 2016-12-06 18:20 +0100
                Re: Enabling peer to peer device transactions for PCIe devices Jason Gunthorpe <jgunthorpe@obsidianresearch.com> - 2016-12-05 19:10 +0100
      RE: Enabling peer to peer device transactions for PCIe devices "Deucher, Alexander" <Alexander.Deucher@amd.com> - 2016-11-30 18:50 +0100
    Re: Enabling peer to peer device transactions for PCIe devices Haggai Eran <haggaie@mellanox.com> - 2016-11-28 21:00 +0100
  Re: Enabling peer to peer device transactions for PCIe devices Haggai Eran <haggaie@mellanox.com> - 2016-11-28 19:40 +0100

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