[PATCH] RFC: ARM: fix the uaccess crash on PB11MPCore

[Neil Armstrong]

On 07/11/2016 07:08 PM, Linus Walleij wrote:
> The following patch was sketched by Russell in response to my
> crashes on the PB11MPCore after the patch for software-based
> priviledged no access support for ARMv8.1. See this thread:
> http://marc.info/?l=linux-arm-kernel&m=144051749807214&w=2
> 
> I am unsure what is going on, I suspect everyone involved in
> the discussion is. I just want to repost this to get the
> discussion restarted, as I still have to apply this patch
> with every kernel iteration to get my PB11MPCore Realview
> running.
> 
> I also know that Oxnas has actual, mass-deployed NAS (PogoPlug
> Pro variants) using PB11MPCore, and that they may or may not
> be seeing the same issue so I want their feedback on this: do
> you or do you not see this with mainline, or have you not even
> tested?
> 
> Cc: Russell King <linux at armlinux.org.uk>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Neil Armstrong <narmstrong at baylibre.com>
> Fixes: a5e090acbf54 ("ARM: software-based priviledged-no-access support")
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
>  arch/arm/kernel/smp_tlb.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Hi Linus, Russell, Arnd,

I made a quick port ox OX820 over v4.8-rc4 and when enabling CONFIG_CPU_SW_DOMAIN_PAN
I get the following trace at boot time :
[    1.690000] Unable to handle kernel paging request at virtual address b6f23684
[    1.690000] Unable to handle kernel paging request at virtual address b6f95ef4
[    1.690000] pgd = c281c000
[    1.690000] [b6f95ef4] *pgd=62821831, *pte=00000000, *ppte=00000000
[    1.690000] Internal error: Oops: 81f [#1] SMP ARM
[    1.690000] Modules linked in:
[    1.690000] CPU: 1 PID: 65 Comm: mount Not tainted 4.8.0-rc4-00001-g0e9c45d-dirty #22
[    1.690000] Hardware name: Generic DT based system
[    1.690000] task: c2aad860 task.stack: c2814000
[    1.690000] PC is at ipi_flush_tlb_page+0x34/0x44
[    1.690000] LR is at on_each_cpu_mask+0x58/0x60
[    1.690000] pc : [<c010d3dc>]    lr : [<c017d584>]    psr: 20000193
[    1.690000] sp : c2815da0  ip : 00000002  fp : 00067c40
[    1.690000] r10: c0702744  r9 : 67c4079f  r8 : 67c9e75f
[    1.690000] r7 : c2815dbc  r6 : c010d3a8  r5 : c2816164  r4 : 20000113
[    1.690000] r3 : 00000000  r2 : b6f95003  r1 : 00000003  r0 : 00000003
[    1.690000] Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
[    1.690000] Control: 00c5787d  Table: 6281c00a  DAC: 00000051
[    1.690000] Process mount (pid: 65, stack limit = 0xc2814190)
[    1.690000] Stack: (0xc2815da0 to 0xc2816000)
[...]
[    1.690000] ---[ end trace 8f1207a6d611da09 ]---

When applying this patch, it solved the issue.

Tested-by: Neil Armstrong <narmstrong at baylibre.com>

Neil