On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>