Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io memory.

From	Dan Williams <dan.j.williams@intel.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io memory.
Date	2017-04-03 23:50 +0200
Message-ID	<tsi1j-40v-9@gated-at.bofh.it> (permalink)
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On Mon, Apr 3, 2017 at 2:20 PM, Logan Gunthorpe <logang@deltatee.com> wrote:
> Hi Christoph,
>
> What are your thoughts on an approach like the following untested
> draft patch.
>
> The patch (if fleshed out) makes it so iomem can be used in an sgl
> and WARN_ONs will occur in places where drivers attempt to access
> iomem directly through the sgl.
>
> I'd also probably create a p2pmem_alloc_sgl helper function so driver
> writers wouldn't have to mess with sg_set_iomem_page.
>
> With all that in place, it should be relatively safe for drivers to
> implement p2pmem even though we'd still technically be violating the
> __iomem boundary in some places.

Just reacting to this mail, I still haven't had a chance to take a
look at the rest of the series.

The pfn_t type was invented to carry extra type and page lookup
information about the memory behind a given pfn. At first glance that
seems a more natural place to carry an indication that this is an
"I/O" pfn.

Thread

[RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
  [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
    Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Sinan Kaya <okaya@codeaurora.org> - 2017-03-31 20:50 +0200
      Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 23:30 +0200
        Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Sinan Kaya <okaya@codeaurora.org> - 2017-03-31 23:40 +0200
          Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-04-01 00:50 +0200
            Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Sinan Kaya <okaya@codeaurora.org> - 2017-04-01 02:00 +0200
              Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-04-01 04:00 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device okaya@codeaurora.org - 2017-04-01 04:20 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-04-02 00:20 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Sinan Kaya <okaya@codeaurora.org> - 2017-04-02 04:30 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-04-02 19:30 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Sinan Kaya <okaya@codeaurora.org> - 2017-04-02 23:10 +0200
                Re: [RFC 1/8] Introduce Peer-to-Peer memory (p2pmem) device Logan Gunthorpe <logang@deltatee.com> - 2017-04-03 06:30 +0200
  [RFC 4/8] p2pmem: Add debugfs "stats" file Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
    Re: [RFC 4/8] p2pmem: Add debugfs "stats" file Sagi Grimberg <sagi@grimberg.me> - 2017-04-04 12:50 +0200
      Re: [RFC 4/8] p2pmem: Add debugfs "stats" file Logan Gunthorpe <logang@deltatee.com> - 2017-04-04 19:30 +0200
      RE: [RFC 4/8] p2pmem: Add debugfs "stats" file "Steve Wise" <swise@opengridcomputing.com> - 2017-04-05 18:20 +0200
  [RFC 2/8] cxgb4: setup pcie memory window 4 and create p2pmem region Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
    Re: [RFC 2/8] cxgb4: setup pcie memory window 4 and create p2pmem  region Sagi Grimberg <sagi@grimberg.me> - 2017-04-04 12:50 +0200
      Re: [RFC 2/8] cxgb4: setup pcie memory window 4 and create p2pmem  region Logan Gunthorpe <logang@deltatee.com> - 2017-04-04 18:00 +0200
      RE: [RFC 2/8] cxgb4: setup pcie memory window 4 and create p2pmem region "Steve Wise" <swise@opengridcomputing.com> - 2017-04-05 18:20 +0200
  [RFC 5/8] scatterlist: Modify SG copy functions to support io memory. Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
    Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Christoph Hellwig <hch@infradead.org> - 2017-03-31 09:20 +0200
      Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 17:50 +0200
        Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Logan Gunthorpe <logang@deltatee.com> - 2017-04-03 23:30 +0200
          Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io memory. Dan Williams <dan.j.williams@intel.com> - 2017-04-03 23:50 +0200
            Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Logan Gunthorpe <logang@deltatee.com> - 2017-04-04 00:20 +0200
              Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io memory. Dan Williams <dan.j.williams@intel.com> - 2017-04-04 00:50 +0200
                Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Logan Gunthorpe <logang@deltatee.com> - 2017-04-04 01:20 +0200
                Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io memory. Dan Williams <dan.j.williams@intel.com> - 2017-04-04 02:10 +0200
                Re: [RFC 5/8] scatterlist: Modify SG copy functions to support io  memory. Logan Gunthorpe <logang@deltatee.com> - 2017-04-07 20:00 +0200
  [RFC 8/8] p2pmem: Added char device user interface Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200
  [RFC 7/8] p2pmem: Support device removal Logan Gunthorpe <logang@deltatee.com> - 2017-03-31 00:20 +0200

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