Messages in this thread | | | Subject | Re: mainline/master bisection: baseline.login on meson-sm1-khadas-vim3l | From | Guillaume Tucker <> | Date | Wed, 24 Feb 2021 09:26:59 +0000 |
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On 24/02/2021 08:52, Marc Zyngier wrote: > On Tue, 23 Feb 2021 21:03:52 +0000, > Guillaume Tucker <guillaume.tucker@collabora.com> wrote: >> >> On 23/02/2021 14:18, Marc Zyngier wrote: >>> Hi Guillaume, >>> >>> On Tue, 23 Feb 2021 09:46:30 +0000, >>> Guillaume Tucker <guillaume.tucker@collabora.com> wrote: >>>> >>>> Hello Marc, >>>> >>>> Please see the bisection report below about a boot failure on >>>> meson-sm1-khadas-vim3l on mainline. It seems to only be >>>> affecting kernels built with CONFIG_ARM64_64K_PAGES=y. >>>> >>>> Reports aren't automatically sent to the public while we're >>>> trialing new bisection features on kernelci.org but this one >>>> looks valid. >>>> >>>> There's no output in the log, so the kernel is most likely >>>> crashing early. Some more details can be found here: >>>> >>>> https://kernelci.org/test/case/id/6034bed3b344e2860daddcc8/ >>>> >>>> Please let us know if you need any help to debug the issue or try >>>> a fix on this platform. >>> >>> Thanks for the heads up. >>> >>> There is actually a fundamental problem with the patch you bisected >>> to: it provides no guarantee that the point where we enable the EL2 >>> MMU is in the idmap and, as it turns out, the code we're running from >>> disappears from under our feet, leading to a translation fault we're >>> not prepared to handle. >>> >>> How does it work with 4kB pages? Luck. >> >> There may be a fascinating explanation for it, but luck works >> too. It really seems to be booting happily with 4k pages: >> >> https://kernelci.org/test/plan/id/60347b358de339d1b7addcc5/ > > Oh, I know it boots fine with 4k, that's what I used everywhere. > We're just lucky that the bit of code that deals with the MMU happens > to *also* be in the idmap. With 64k pages, it gets pushed further down > the line, and bad things happen. Short of explicit statements in the > code, luck rules.
OK I see that now, thanks for the explanation.
>>> Do you mind giving the patch below a go? It does work on my vim3l and >>> on a FVP, so odds are that it will solve it for you too. >> >> Sure, and that worked here as well: >> >> http://lava.baylibre.com:10080/scheduler/job/752416 >> >> and here's the test branch where I applied your fix, for >> completeness: >> >> https://gitlab.collabora.com/gtucker/linux/-/commits/v5.11-vim3l-vhe/ > > Awesome. thanks for having tested it. > >> As always, if you do send a patch with the fix, please give some >> credit to the bot: >> >> Reported-by: "kernelci.org bot" <bot@kernelci.org> > > Will do. Mind if I credit you too for the testing?
Sure:
Tested-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Thanks, Guillaume
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