Re: [PATCH 3/4] target/ppc: Move common check in machne check handlers to a function

[Nicholas Piggin]

On Fri Jun 23, 2023 at 11:20 PM AEST, Fabiano Rosas wrote:
> Nicholas Piggin <npiggin@gmail.com> writes:
>
> > From: BALATON Zoltan <balaton@eik.bme.hu>
> >
> > All powerpc exception handlers share some code when handling machine
> > check exceptions. Move this to a common function.
> >
>
> Maybe Machine Check is simple enough, but this kind of sharing of code
> has historically caused pain when people want to change something for
> the modern cpus and end up affecting the old cpus by mistake.
>
> There is also the inverse scenario where someone has access to the old
> HW and just want to make an one-off contribution, but the community gets
> insecure about it because it could also affect the new cpus.
>
> Then comes the obvious "solution" which is to bring in an artificial
> identifier (excp. model) to be able to have conditional code inside the
> common function. And that causes problems because no one really knows
> how it maps to actual hardware/ISA.
>
> No objection, just a little cautionary tale. =)

Thanks Fabiano, good point. I know you spent a lot of work on untangling
this mess. I'll think a bit more about it. Seems we need to at least make
a few fixes first before we can turn this on for upstream.

Thanks,
Nick