On Mon, Apr 3, 2017 at 2:20 PM, Logan Gunthorpe <logang@xxxxxxxxxxxx> 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.
