[PATCH v3 4/4] ARM: Implement PAN for LPAE by TTBR0 page table walks disablement

[Geert Uytterhoeven]

Hi Linus,

On Mon, May 13, 2024 at 10:29 PM Linus Walleij <linus.walleij at linaro.org> wrote:
> On Mon, May 13, 2024 at 9:58 PM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> > On Mon, May 13, 2024 at 9:24 PM Linus Walleij <linus.walleij at linaro.org> wrote:
> > > On Tue, May 7, 2024 at 3:10 PM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> > > > Thanks for your patch, which is now commit 7af5b901e84743c6 ("ARM:
> > > > 9358/2: Implement PAN for LPAE by TTBR0 page table walks disablement")
> > > > in arm/for-next (next-20240502 and later).
> > > >
> > > > On Koelsch (R-Car M2-W with dual Cortex A15) with LPAE enabled:
> > > >
> > > >     Run /sbin/init as init process
> > > >       with arguments:
> > > >         /sbin/init
> > > >       with environment:
> > > >         HOME=/
> > > >         TERM=linux
> > > >     Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
> > > >     CPU: 1 PID: 1 Comm: init Tainted: G        W        N
> > > > 6.9.0-rc1-koelsch-00004-g7af5b901e847 #1930
> > > >     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> > > >     Call trace:
> > > >      unwind_backtrace from show_stack+0x10/0x14
> > > >      show_stack from dump_stack_lvl+0x78/0xa8
> > > >      dump_stack_lvl from panic+0x118/0x398
> > > >      panic from do_exit+0x1ec/0x938
> > > >      do_exit from sys_exit_group+0x0/0x10
> > > >     ---[ end Kernel panic - not syncing: Attempted to kill init!
> > > > exitcode=0x00000004 ]---
> > > >
> > > > Disabling LPAE fixes the issue.
> > >
> > > How annoying. I guess it doesn't help you that it works like a charm on
> > > Versatile Express in QEMU, and also actually tested on the real
> > > hardware. (Dual Cortex-A9).
> >
> > Interesting. AFAIK Cortex-A9 does not support LPAE?
>
> Allright I was rambling, what I used (albeit early on) was
> STMicro STM32MP157 which has Cortex-A7.

I can reproduce the issue on Cortex-A7 (R-Car E2), too.

CONFIG_ARM_LPAE=y
CONFIG_CPU_TTBR0_PAN=y

> > > So init is not executing, which userspace is this? I was  just testing
> > > with busybox so far, maybe I need to test on something
> > > bigger?
> > >
> > > Do you have your ARMv7 file system available in an image or so
> > > I can test it on Versatile Express?
> >
> > It's just a Debian nfsroot.
>
> OK I tried with a vanilla ArchLinuxARM rootfs which uses systemd
> and all that hoopla and it boots just fine.
>
> So I'm a bit lost here.

I sent you a small initramfs by PM.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds