Re: [PATCH v2 4/8] ppc/spapr: Fix FWNMI machine check interrupt delivery

[Nicholas Piggin]

Cédric Le Goater's on March 17, 2020 3:59 am:
> On 3/16/20 3:26 PM, Nicholas Piggin wrote:
>> FWNMI machine check delivery misses a few things that will make it fail
>> with TCG at least (which we would like to allow in future to improve
>> testing).
> 
> I don't understand which issues are addressed in the patch.

The existing code does not compute hflags, at least.

There's a few possible other things, I didn't dig into qemu enough
to know if they might be a problem (e.g., reservation and TLB). I
figure it's better to keep these consistent.

Keep in mind this is a bit academic right now, because we can't
(AFAIKS) inject an MCE from TCG. It would be good to wire that up,
but I didn't get to it.

>> It's not nice to scatter interrupt delivery logic around the tree, so
>> move it to excp_helper.c and share code where possible.
> 
> It looks correct but this is touching the ugliest routine in the QEMU 
> PPC universe. I would split the patch in two to introduce the helper
> powerpc_set_excp_state().
> 
> It does not seem to need to be an inline also.

Yeah it's all pretty ugly. I didn't yet find a nice way to do
split things up that did not require a lot of code churn, but that
can come later.

Inline was just because powerpc_excp is inline, I didn't want to
change behaviour too much there (it obviously wants to do a lot of
constant propagation but maybe only on the case statement). Anyway
I just wanted to be minimal for now, it could be changed.

Thanks,
Nick