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


From: David Gibson
Subject: Re: [PATCH v2 4/8] ppc/spapr: Fix FWNMI machine check interrupt delivery
Date: Tue, 17 Mar 2020 10:27:00 +1100

On Tue, Mar 17, 2020 at 09:19:57AM +1000, Nicholas Piggin wrote:
> 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.

Yeah, I definitely want to get this in, so despite imperfections that
could probably be polished with time, I've applied to ppc-for-5.0.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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