[PATCH v3 7/7] ARM: implement support for vmap'ed stacks

[Arnd Bergmann]

On Wed, Nov 17, 2021 at 9:36 AM Tony Lindgren <tony at atomide.com> wrote:
> * Ard Biesheuvel <ardb at kernel.org> [211117 08:29]:
> >
> > Thanks Tony, that is very helpful. I have a Beaglebone white somewhere
> > so I'll try and reproduce it locally as well.
>
> I think with Beaglebone you may hit this only with suspend/resume if at
> all. On am335x cpuidle is not shutting down the CPU. And only some models
> will suspend to deeper idle states as it depends on the PMIC.
>
> If you have some test patch to try, just let me know.

I looked at how the sleep code is called and found that cpu_suspend()/
__cpu_suspend() has interesting manipulation of the stack pointer to
call the platform specific function with a simple 1:1 page table,
I would expect the problem somewhere in there, haven't pinpointed
the exact line yet, but if any of that code tries to local the physical
address of the stack using virt_to_phys or its asm equivalent, this
fails for a vmap stack.

        Arnd