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Date: Mon, 30 Jan 2012 11:19:18 -0800 From: Roland Dreier <roland@...nel.org> To: Jason Gunthorpe <jgunthorpe@...idianresearch.com> Cc: Hugh Dickins <hughd@...gle.com>, linux-rdma@...r.kernel.org, Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH/RFC G-U-P experts] IB/umem: Modernize our get_user_pages() parameters On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe <jgunthorpe@...idianresearch.com> wrote: > I know accessing system memory (eg obtained via mmap on > /sys/bus/pci/devices/0000:00:02.0/resource0) has been asked for in the > past, and IIRC, the problem was that some of the common code, (GUP?) > errored on these maps. I don't know if Roland's case is similar. I think the problem there is that this is done via remap_pfn_range() or similar, and the mapping has no underlying pages at all. So we would need a new interface that gives us different information for such cases. This is quite a bit trickier since I don't think the DMA API even has a way to express getting a "device A" bus address for some memory that is in a BAR for "device B". So I'm not trying to address this case (yet). First I'd like to deal with as many flavors of page-backed mappings as I can. - R. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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