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Subject: Re: [PATCH 18/19] KVM: PPC: Book3S HV: add passthrough support
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@ozlabs.org>
Date: Thu, 24 Jan 2019 08:25:15 +1100
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Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org,
 =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>,
 linuxppc-dev@lists.ozlabs.org, David Gibson <david@gibson.dropbear.id.au>
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On Wed, 2019-01-23 at 21:30 +1100, Paul Mackerras wrote:
> > Afaik bcs we change the mapping to point to the real HW irq ESB page
> > instead of the "IPI" that was there at VM init time.
> 
> So that makes it sound like there is a whole lot going on that hasn't
> even been hinted at in the patch descriptions...  It sounds like we
> need a good description of how all this works and fits together
> somewhere under Documentation/.
> 
> In any case we need much more informative patch descriptions.  I
> realize that it's all currently in Cedric's head, but I bet that in
> two or three years' time when we come to try to debug something, it
> won't be in anyone's head...

The main problem is understanding XIVE itself. It's not realistic to
ask Cedric to write a proper documentation for XIVE as part of the
patch series, but sadly IBM doesn't have a good one to provide either.

Ben.