Re: arm64: unhandled level 0 translation fault

[Geert Uytterhoeven]

Hi Dave,

On Thu, Dec 14, 2017 at 4:24 PM, Dave P Martin <Dave.Martin@xxxxxxx> wrote:
> On Thu, Dec 14, 2017 at 02:34:50PM +0000, Geert Uytterhoeven wrote:
>> On Tue, Dec 12, 2017 at 11:20 AM, Geert Uytterhoeven
>> <geert@xxxxxxxxxxxxxx> wrote:
>> > During userspace (Debian jessie NFS root) boot on arm64:
>> >
>> > rpcbind[1083]: unhandled level 0 translation fault (11) at 0x00000008,
>> > esr 0x92000004, in dash[aaaaadf77000+1a000]
>> > CPU: 0 PID: 1083 Comm: rpcbind Not tainted
>> > 4.15.0-rc3-arm64-renesas-02176-g14f9a1826e48e355 #51
>> > Hardware name: Renesas Salvator-X 2nd version board based on r8a7795 ES2.0+ (DT)
>>
>> This is a quad Cortex A57.
>>
>> > pstate: 80000000 (Nzcv daif -PAN -UAO)
>> > pc : 0xaaaaadf8a51c
>> > lr : 0xaaaaadf8ac08
>> > sp : 0000ffffcffeac00
>> > x29: 0000ffffcffeac00 x28: 0000aaaaadfa1000
>> > x27: 0000ffffcffebf7c x26: 0000ffffcffead20
>> > x25: 0000aaaacea1c5f0 x24: 0000000000000000
>> > x23: 0000aaaaadfa1000 x22: 0000aaaaadfa1000
>> > x21: 0000000000000000 x20: 0000000000000008
>> > x19: 0000000000000000 x18: 0000ffffcffeb500
>> > x17: 0000ffffa22babfc x16: 0000aaaaadfa1ae8
>> > x15: 0000ffffa2363588 x14: ffffffffffffffff
>> > x13: 0000000000000020 x12: 0000000000000010
>> > x11: 0101010101010101 x10: 0000aaaaadfa1000
>> > x9 : 00000000ffffff81 x8 : 0000aaaaadfa2000
>> > x7 : 0000000000000000 x6 : 0000000000000000
>> > x5 : 0000aaaaadfa2338 x4 : 0000aaaaadfa2000
>> > x3 : 0000aaaaadfa2338 x2 : 0000000000000000
>> > x1 : 0000aaaaadfa28b0 x0 : 0000aaaaadfa4c30
>> >
>> > Sometimes it happens with other processes, but the main address, esr, and
>> > pstate values are always the same.
>> >
>> > I regularly run arm64/for-next/core (through bi-weekly renesas-drivers
>> > releases, so the last time was two weeks ago), but never saw the issue
>> > before until today, so probably v4.15-rc1 is OK.
>> > Unfortunately it doesn't happen during every boot, which makes it
>> > cumbersome to bisect.
>> >
>> > My first guess was UNMAP_KERNEL_AT_EL0, but even after disabling that,
>> > and even without today's arm64/for-next/core merged in, I still managed to
>> > reproduce the issue, so I believe it was introduced in v4.15-rc2 or
>> > v4.15-rc3.
>> >
>> > Once, when the kernel message above wasn't shown, I got an error from
>> > userspace, which may be related:
>> > *** Error in `/bin/sh': free(): invalid pointer: 0x0000aaaadd970988 ***
>>
>> With more boots (10 instead of 6) to declare a kernel good, I bisected this
>> to commit 9de52a755cfb6da5 ("arm64: fpsimd: Fix failure to restore FPSIMD
>> state after signals").
>>
>> Reverting that commit on top of v4.15-rc3 fixed the issue for me.
>
> Good work on the bisect -- I'll need to have a think about this...
>
> That patch fixes a genuine problem so we can't just revert it.
>
> What if you revert _just this function_ back to what it was in v4.14?

With fpsimd_update_current_state() reverted to v4.14, and

-               __this_cpu_write(fpsimd_last_state, st);
+               __this_cpu_write(fpsimd_last_state.st, st);

to make it build, the problem seems to be fixed, too.

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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