Linux kernel regressions
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* Re: [i915] b12d691ea5: kernel_BUG_at_mm/memory.c
       [not found]   ` <20210519133330.GA14452@lst.de>
@ 2021-05-19 15:00     ` Kalle Valo
  2021-05-19 16:11       ` Linus Torvalds
  0 siblings, 1 reply; 3+ messages in thread
From: Kalle Valo @ 2021-05-19 15:00 UTC (permalink / raw)
  To: Christoph Hellwig
  Cc: Linus Torvalds, kernel test robot, Thomas Hellström,
	Serge Belyshev, Chris Wilson, Daniel Vetter, Jani Nikula,
	Joonas Lahtinen, Peter Zijlstra, Rodrigo Vivi, Andrew Morton,
	LKML, lkp, kernel test robot, regressions

Christoph Hellwig <hch@lst.de> writes:

> 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.

Yes, please revert it if there's no quick fix. On my Dell XPS 13 9310
laptop (with Debian 10) X won't start until I revert commit
b12d691ea5e0, so this is a major issue.

Also adding the new regressions list, as this is an i915 regression
introduced in v5.13-rc1.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [i915] b12d691ea5: kernel_BUG_at_mm/memory.c
  2021-05-19 15:00     ` [i915] b12d691ea5: kernel_BUG_at_mm/memory.c Kalle Valo
@ 2021-05-19 16:11       ` Linus Torvalds
  2021-05-19 16:31         ` Linus Torvalds
  0 siblings, 1 reply; 3+ messages in thread
From: Linus Torvalds @ 2021-05-19 16:11 UTC (permalink / raw)
  To: Kalle Valo
  Cc: Christoph Hellwig, kernel test robot, Thomas Hellström,
	Serge Belyshev, Chris Wilson, Daniel Vetter, Jani Nikula,
	Joonas Lahtinen, Peter Zijlstra, Rodrigo Vivi, Andrew Morton,
	LKML, lkp, kernel test robot, regressions

On Wed, May 19, 2021 at 5:00 AM Kalle Valo <kvalo@codeaurora.org> wrote:
>
> Christoph Hellwig <hch@lst.de> writes:
>
> > On Tue, May 18, 2021 at 04:58:31PM -1000, Linus Torvalds wrote:
> >>
> >> 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.
>
> Yes, please revert it if there's no quick fix. On my Dell XPS 13 9310
> laptop (with Debian 10) X won't start until I revert commit
> b12d691ea5e0, so this is a major issue.

Reverted.

                 Linus

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [i915] b12d691ea5: kernel_BUG_at_mm/memory.c
  2021-05-19 16:11       ` Linus Torvalds
@ 2021-05-19 16:31         ` Linus Torvalds
  0 siblings, 0 replies; 3+ messages in thread
From: Linus Torvalds @ 2021-05-19 16:31 UTC (permalink / raw)
  To: Kalle Valo
  Cc: Christoph Hellwig, kernel test robot, Thomas Hellström,
	Serge Belyshev, Chris Wilson, Daniel Vetter, Jani Nikula,
	Joonas Lahtinen, Peter Zijlstra, Rodrigo Vivi, Andrew Morton,
	LKML, lkp, kernel test robot, regressions

On Wed, May 19, 2021 at 6:11 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, May 19, 2021 at 5:00 AM Kalle Valo <kvalo@codeaurora.org> wrote:
> >
> > Christoph Hellwig <hch@lst.de> writes:
> >
> > > On Tue, May 18, 2021 at 04:58:31PM -1000, Linus Torvalds wrote:
> > >>
> > >> 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.
> >
> > Yes, please revert it if there's no quick fix. On my Dell XPS 13 9310
> > laptop (with Debian 10) X won't start until I revert commit
> > b12d691ea5e0, so this is a major issue.
>
> Reverted.

Oh, and Christoph - there were a couple of preparatory patches before
that one. They all looked syntactic to me, but it might be best to
check that reverting just this one commit is ok?

                   Linus

^ permalink raw reply	[flat|nested] 3+ messages in thread

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     [not found] ` <CAHk-=whcr5M=4Mz2ydu4XtxTL_34WkXPnmFmA4f8r+ELXDC6hg@mail.gmail.com>
     [not found]   ` <20210519133330.GA14452@lst.de>
2021-05-19 15:00     ` [i915] b12d691ea5: kernel_BUG_at_mm/memory.c Kalle Valo
2021-05-19 16:11       ` Linus Torvalds
2021-05-19 16:31         ` Linus Torvalds

Linux kernel regressions

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