[PATCH 18/19] KVM: PPC: Book3S HV: add passthrough support

[Cédric Le Goater]

On 1/23/19 10:25 PM, Benjamin Herrenschmidt wrote:
> 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.

QEMU has a preliminary introduction we could use :

https://git.qemu.org/?p=qemu.git;a=blob;f=include/hw/ppc/xive.h;h=ec23253ba448e25c621356b55a7777119a738f8e;hb=HEAD

With some extensions for sPAPR and KVM, the resulting file could 
be moved to the Linux documentation directory. This would be an
iterative process over time of course. 

Cheers,

C.