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Date:   Tue, 12 Jan 2021 14:06:56 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Guillaume Tucker <guillaume.tucker@...labora.com>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        kernelci-results-staging@...ups.io,
        "kernelci-results@...ups.io" <kernelci-results@...ups.io>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>, Baoquan He <bhe@...hat.com>
Subject: Re: kernelci/staging-next bisection: sleep.login on
 rk3288-rock2-square #2286-staging

On Tue, Jan 12, 2021 at 10:53:45AM +0000, Guillaume Tucker wrote:
> On 05/01/2021 09:13, Mike Rapoport wrote:
> > On Sun, Jan 03, 2021 at 03:09:14PM -0500, Andrea Arcangeli wrote:
> >> Hello Mike,
> >>
> >> On Sun, Jan 03, 2021 at 03:47:53PM +0200, Mike Rapoport wrote:
> >>> Thanks for the logs, it seems that implicitly adding reserved regions to
> >>> memblock.memory wasn't that bright idea :)
> >>
> >> Would it be possible to somehow clean up the hack then?
> >>
> >> The only difference between the clean solution and the hack is that
> >> the hack intended to achieved the exact same, but without adding the
> >> reserved regions to memblock.memory.
> > 
> > I didn't consider adding reserved regions to memblock.memory as a clean
> > solution, this was still a hack, but I didn't think that things are that
> > fragile.
> > 
> > I still think we cannot rely on memblock.reserved to detect
> > memory/zone/node sizes and the boot failure reported here confirms this.
> >  
> >> The comment on that problematic area says the reserved area cannot be
> >> used for DMA because of some unexplained hw issue, and that doing so
> >> prevents booting, but since the area got reserved, even with the clean
> >> solution, it shouldn't have never been used for DMA?
> >>
> >> So I can only imagine that the physical memory region is way more
> >> problematic than just for DMA. It sounds like that anything that
> >> touches it, including the CPU, will hang the system, not just DMA. It
> >> sounds somewhat similar to the other e820 direct mapping issue on x86?
> > 
> > My understanding is that the boot failed because when I implicitly added
> > the reserved region to memblock.memory the memory size seen by
> > free_area_init() jumped from 2G to 4G because the reserved area was close
> > to 4G. The very first allocation would get a chunk from slightly below of
> > 4G and as there is no real memory there, the kernel would crash.
> >  
> >> If you want to test the hack on the arm board to check if it boots you
> >> can use the below commit:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/andrea/aa.git/commit/?id=c3ea2633015104ce0df33dcddbc36f57de1392bc
> > 
> > My take is your solution would boot with this memory configuration, but I
> > still don't think that using memblock.reserved for zone/node sizing is
> > correct.
> 
> The rk3288 platform has now been failing to boot for nearly a
> month on linux-next:
> 
>   https://kernelci.org/test/case/id/5ffbed0a31ad81239bc94cdb/
> 
> Until a fix or a new version of this patch is made, would it be
> possible to drop it or revert it so the platform become usable
> again?

There is a new version of these patches:

https://lore.kernel.org/lkml/20210111194017.22696-1-rppt@kernel.org

It's going to be in linux-next as soon as Andrew pushes mmotm.
 
> Or if you want, I can make a cleaned-up version of my hack to
> ignore the problematic region if you still need your patch to be
> on linux-next, but that would probably be less than ideal.
> 
> Thanks,
> Guillaume

-- 
Sincerely yours,
Mike.

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