On 13/10/2017 19:17, Michal Hocko wrote: > On Fri 13-10-17 10:56:13, Cristopher Lameter wrote: >> On Fri, 13 Oct 2017, Michal Hocko wrote: >> >>>> There is a generic posix interface that could we used for a variety >>>> of specific hardware dependent use cases. >>> Yes you wrote that already and my counter argument was that this >>> generic posix interface shouldn't bypass virtual memory abstraction. >> It does do that? In what way? > availability of the virtual address space depends on the availability > of the same sized contiguous physical memory range. That sounds like > the abstraction is gone to large part to me. In what way? userspace users will still be working with virtual memory. > >>>> There are numerous RDMA devices that would all need the mmap >>>> implementation. And this covers only the needs of one subsystem. >>>> There are other use cases. >>> That doesn't prevent providing a library function which could be >>> reused by all those drivers. Nothing really too much different from >>> remap_pfn_range. >> And then in all the other use cases as well. It would be much easier >> if mmap could give you the memory you need instead of havig numerous >> drivers improvise on their own. This is in particular also useful for >> numerous embedded use cases where you need contiguous memory. > But a generic implementation would have to deal with many issues as > already mentioned. If you make this driver specific you can have > access control based on fd etc... I really fail to see how this is any > different from remap_pfn_range. Why have several driver specific implementation if you can generalize the idea and implement an already existing POSIX standard? -- Guy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
