Messages in this thread | | | From | Roland Dreier <> | Date | Mon, 30 Jan 2012 11:19:18 -0800 | Subject | Re: [PATCH/RFC G-U-P experts] IB/umem: Modernize our get_user_pages() parameters |
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On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe <jgunthorpe@obsidianresearch.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.
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