[PATCH] arc: Re-enable MMU upon die()

[Jose Abreu]

Hi Alexey,

On 01-09-2017 12:48, Alexey Brodkin wrote:
> Hi Jose,
>
> On Fri, 2017-09-01 at 12:39 +0100, Jose Abreu wrote:
>> I recently came upon a scenario where I would get a double fault
>> after a machine check error. It turns out that for Ksymbol lookup
>> to work with modules we need to have MMU enabled because module
>> address is mapped in the cached space.
>>
>> This patch re-enables the MMU before start printing the stacktrace
>> making stacktracing of modules work upon a fatal exception.
> I'm wondering how do we end up with MMU disabled?
> From ARC700 databook I cannot find any condition on which MMU could be
> silently disabled by hardware and IIRC there's no code in Linux kernel
> that disables MMU.

According to ARC 700 databook a machine check exception causes
Global TLB enable to be cleared. (See ARC 700 databook, page 687).

Best regards,
Jose Miguel Abreu

>
> -Alexey