Messages in this thread | | | Date | Wed, 19 May 2021 15:33:30 +0200 | From | Christoph Hellwig <> | Subject | Re: [i915] b12d691ea5: kernel_BUG_at_mm/memory.c |
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On Tue, May 18, 2021 at 04:58:31PM -1000, Linus Torvalds wrote: > On Tue, May 18, 2021 at 4:26 PM kernel test robot <oliver.sang@intel.com> wrote: > > > > commit: b12d691ea5e01db42ccf3b4207e57cb3ce7cfe91 ("i915: fix remap_io_sg to verify the pgprot") > > [...] > > [ 778.550996] kernel BUG at mm/memory.c:2183! > > [ 778.559015] RIP: 0010:remap_pfn_range_notrack (kbuild/src/consumer/mm/memory.c:2183 kbuild/src/consumer/mm/memory.c:2211 kbuild/src/consumer/mm/memory.c:2233 kbuild/src/consumer/mm/memory.c:2255 kbuild/src/consumer/mm/memory.c:2311) > > [ 778.688951] remap_pfn_range (kbuild/src/consumer/mm/memory.c:2342) > > [ 778.692700] remap_io_sg (kbuild/src/consumer/drivers/gpu/drm/i915/i915_mm.c:71) i915 > > Yeah, so that BUG_ON() checks that theer isn't any old mapping there. > > You can't just remap over an old one, but it does seem like that is > exactly what commit b12d691ea5e0 ("i915: fix remap_io_sg to verify the > pgprot") ends up doing. > > So the code used to just do "apply_to_page_range()", which admittedly > was odd too. But it didn't mind having old mappings and re-applying > something over them. > > Converting it to use remap_pfn_range() does look better, but it kind > of depends on it ever being done *once*. But the caller seems to very > much remap the whole vmsa at fault time, so... > > I don't know what the right thing to do here is, because I don't know > the invalidation logic and when faults happen. > > I see that there is another thread about different issues on the > intel-gfx list. Adding a few people to this kernel test robot thread > too. > > I'd be inclined to revert the commits as "not ready yet", but it would > be better if somebody can go "yeah, this should be done properly like > X".
I think reverting just this commit for now is the best thing.
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