Messages in this thread | | | Date | Wed, 24 Feb 2021 08:52:30 +0000 | From | Marc Zyngier <> | Subject | Re: mainline/master bisection: baseline.login on meson-sm1-khadas-vim3l |
| |
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.
> > > 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?
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
| |