Re: [Qemu-devel] [RFC PATCH v2 01/21] ppc/xive: introduce a skeleton for the sPAPR XIVE interrupt controller

[Benjamin Herrenschmidt]

On Tue, 2017-09-26 at 13:54 +1000, David Gibson wrote:
> > > 
> > > Which ones?  My impression was that there needed to be at least #cpus
> > > * #priority-levels EQs, but there could be more than that, 
> > 
> > euh no, not in spapr mode at least. There are 8 queues per cpu.
> 
> Ok.

There's a HW feature of XIVE in DD2.x that I will start exploiting soon
that sacrifices a queue btw, keep that in mind.

We should probably only expose 0...6 to guests, not 0...7.

> > > so it was no longer as tightly bound to the number if "interrupt 
> > > servers"> as xics.
> > 
> > ah. I think I see what you mean, that we could allocate them on the 
> > fly when needed by some hcalls ?
> 
> Not at hcall time, no, but at cpu hot(un)plug time I was wondering if we
> could (de)allocate them then.
> 
> > The other place where I use the nr_targets is to provision the 
> > IRQ numbers for the IPIs but that could probably be done in some 
> > other way, specially it there is a IRQ allocator at the machine
> > level.
> 
> Hm, ok.
>