Re: [PATCH v2] arm64: invalidate TLB just before turning MMU on

From: Qian Cai
Date: Fri Dec 14 2018 - 20:54:03 EST

On 12/14/18 2:23 AM, Ard Biesheuvel wrote:
> On Fri, 14 Dec 2018 at 05:08, Qian Cai <cai@xxxxxx> wrote:
>> Also tried to move the local TLB flush part around a bit inside
>> __cpu_setup(), although it did complete kdump some times, it did trigger
>> "Synchronous Exception" in EFI after a cold-reboot fairly often that
>> seems no way to recover remotely without reinstalling the OS.
> This doesn't make any sense to me. If the system gets into a weird
> state out of cold reboot, how could this code be the culprit? Please
> check your firmware, and try to reproduce the issue on a system that
> doesn't have such defects.

I'll continue investigating those "Synchronous Exception" although it is kind of
hard due to I don't have any source code of the firmware to confirm it is buggy
or not.

I did manage to reproduce this kdump issue on around 5 of those server running a
fairly recent version of the firmware (07/01/2018). I don't have access to other
large CPU machines.