RE: [PATCH V2 4/6] x86/efi: Add efi page fault handler to fixup/recover from page faults caused by firmware

Prakhya, Sai Praneeth
2018-09-03T17:16:01Z

> > The efi specific page fault handler offers us two advantages:
> > 1. Avoid panics/hangs caused by buggy firmware.
> > 2. Shout loud that the firmware is buggy and hence is not a kernel bug.
> >
> > Finally, this new mapping will not impact a reboot from kexec, as
> > kexec is only concerned about runtime memory regions.
>
> No. This is just a horrible hack to make completely bogus firmware work and
> never fixed.
>

Yes, that's true.

> The proper thing to do is to have a minimal page fault handler which does:
>
> 1) Yell loudly if that ever happens
>
> 2) Handles the reboot request gracefully
>
> 3) Freeze and disable the EFI mess for all other cases
>
> That does not require any hackery to make these mappings work from atomic
> context and keeps the mess confined to the EFI code where it belongs.
>
> Ideally we just blacklist the offending system and be done with it.

This makes sense to me. I will implement the above suggested and as said should
avoid the need for making mappings work from atomic context.

Regards,
Sai