On Tue, January 26, 2016 06:00, Sudip Mukherjee wrote: > On Mon, Jan 25, 2016 at 04:06:40PM -0800, Dan Williams wrote: >> It appears devices requiring ZONE_DMA are still prevalent (see link >> below). For this reason the proposal to require turning off ZONE_DMA to >> enable ZONE_DEVICE is untenable in the short term. We want a single >> kernel image to be able to support legacy devices as well as next >> generation persistent memory platforms. >> >> Towards this end, alias ZONE_DMA and ZONE_DEVICE to work around needing >> to maintain a unique zone number for ZONE_DEVICE. Record the geometry >> of ZONE_DMA at init (->init_spanned_pages) and use that information in >> is_zone_device_page() to differentiate pages allocated via >> devm_memremap_pages() vs true ZONE_DMA pages. Otherwise, use the >> simpler definition of is_zone_device_page() when ZONE_DMA is turned off. >> >> Note that this also teaches the memory hot remove path that the zone may >> not have sections for all pfn spans (->zone_dyn_start_pfn). >> >> A user visible implication of this change is potentially an unexpectedly >> high "spanned" value in /proc/zoneinfo for the DMA zone. >> >> Cc: H. Peter Anvin <hpa@xxxxxxxxx> >> Cc: Ingo Molnar <mingo@xxxxxxxxxx> >> Cc: Rik van Riel <riel@xxxxxxxxxx> >> Cc: Mel Gorman <mgorman@xxxxxxx> >> Cc: Jerome Glisse <j.glisse@xxxxxxxxx> >> Cc: Christoph Hellwig <hch@xxxxxx> >> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=110931 >> Fixes: 033fbae988fc ("mm: ZONE_DEVICE for "device memory"") >> Reported-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx> > > It should actually be Reported-by: Mark <markk@xxxxxxxxxxx> > > Hi Mark, > Can you please test this patch available at > https://patchwork.kernel.org/patch/8116991/ > in your setup.. I applied that patch to 4.5-rc1 and it seems to work. At least, there is no error message in dmesg output any more. I didn't actually try using the parallel port (need to find a parallel printer cable). Presumably a parallel printer would work whether DMA is used or not, just slower and using more CPU time in the PIO case. Also, I don't have any hardware that needs CONFIG_ZONE_DEVICE. The config file I used to compile the kernel can be downloaded from https://www.mediafire.com/?1do33bkko41ypo3 if anyone feels like taking a look. Perhaps someone with one of the affected PCI sound cards could also test the patch, since those presumably don't work/build at all without it. Hopefully someone else has a PC with native parallel port to confirm the fix. (Native floppy controller may be another affected device.) Mark -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>