CSD lockup during kexec due to unbounded busy-wait in pl011_console_write_atomic (arm64)

[Marco Elver]

On Wed, 26 Nov 2025 at 16:54, Breno Leitao <leitao at debian.org> wrote:
[..]
> > > Alexander, Marco and Kasan maintainers:
> > >
> > > What is the potential impact of disabling KFENCE during reboot
> > > procedures?
> >
> > But only if CONFIG_KFENCE_STATIC_KEYS is enabled?
> > That would be reasonable, given our recommendation has been to disable
> > CONFIG_KFENCE_STATIC_KEYS since
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4f612ed3f748962cbef1316ff3d323e2b9055b6e
> > in most cases.
> >
> > I believe some low-CPU count systems are still benefiting from it, but
> > in general, I'd advise against it.
>
> Thanks for your review and guidance.
>
> Just to confirm my understanding: You’re okay with me adding this
> notifier specifically for CONFIG_KFENCE_STATIC_KEYS (which is what
> I need), but you would not support adding it for the general case where
> !CONFIG_KFENCE_STATIC_KEYS, correct?

Yes, correct. If there's a real issue with CONFIG_KFENCE_STATIC_KEYS,
it's worth fixing if there are still valid uses for it. But I wouldn't
pessimize the now default mode, which is !CONFIG_KFENCE_STATIC_KEYS,
as it doesn't appear to have this problem.

Thanks,
-- Marco