[PATCH] arm64: fix kernel panic on serror exception caused by user process

[james.morse@arm.com (James Morse)]

Hi hari,

On 17/07/18 14:40, Hari Vyas wrote:
> On Tue, Jul 17, 2018 at 5:18 PM, Mark Rutland <mark.rutland@arm.com> wrote:
>> ... indeed, and this was a bug, which was addressed by ensuring that
>> an uncontainable SError was always fatal.
>>
> If I check commit message for do_serror(), it says some hooks can be
> added to avoid panic.
> ---
> commit a92d4d1454ab8b43b80b89fa31fcedb8821f8164
> Author: Xie XiuQi <xiexiuqi@huawei.com>
> 
> Future patches may change do_serror() to return if the SError
> Interrupt was notification of a
> corrected error
>  --

This is referring to the v8.2 RAS Extensions, which add architect-ed ESR values
to SError. In this example the CPU would use the ESR_ELx.AET bits to describe
the error as something hardware has corrected. e.g. using ecc. (details in
D10.2.39 of the ARM-ARM and [0])
commit 6bf0dcfd7135 ("arm64: kernel: Survive corrected RAS errors notified by
SError") adds these hooks based on the ESR information.

Without the information in the ESR (and a few other registers), we can't know
what the SError means, it has to be fatal.


Thanks,

James

[0]
https://static.docs.arm.com/ddi0587/a/RAS%20Extension-release%20candidate_march_29.pdf