On Tue, 2016-08-23 at 13:42 -0700, Andrew Morton wrote: > On Tue, 23 Aug 2016 12:43:20 -0600 Toshi Kani <toshi.k...@hpe.com> > wrote: > > > > > The following BUG was observed while starting up KVM with nvdimm > > device as memory-backend-file to /dev/dax. > > > > BUG: unable to handle kernel NULL pointer dereference at > > 0000000000000008 > > > > ... > > > > devm_memremap_pages() calls for_each_device_pfn() to walk through > > all pfns in page_map. pfn_first(), however, returns a wrong pfn > > that leaves page->pgmap uninitialized. > > > > Since arch_add_memory() has set up direct mappings to the NVDIMM > > range with altmap, pfn_first() should not modify the start pfn. > > Change pfn_first() to simply return pfn of res->start. > > Which kernel version(s) do you think need fixing?
The fix applies to v4.5 and newer versions. Thanks, -Toshi
