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

[Fabiano Rosas]

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. =)