Re: [PATCH 11/20] spapr: Fix indexing of XICS irqs

[David Gibson]

On Wed, Sep 25, 2019 at 10:17:46PM +0200, Greg Kurz wrote:
> On Wed, 25 Sep 2019 16:45:25 +1000
> David Gibson <address@hidden> wrote:
> 
> > spapr global irq numbers are different from the source numbers on the ICS
> > when using XICS - they're offset by XICS_IRQ_BASE (0x1000).  But
> > spapr_irq_set_irq_xics() was passing through the global irq number to
> > the ICS code unmodified.
> > 
> > We only got away with this because of a counteracting bug - we were
> > incorrectly adjusting the qemu_irq we returned for a requested global irq
> > number.
> > 
> > That approach mostly worked but is very confusing, incorrectly relies on
> > the way the qemu_irq array is allocated, and undermines the intention of
> > having the global array of qemu_irqs for spapr have a consistent meaning
> > regardless of irq backend.
> > 
> > So, fix both set_irq and qemu_irq indexing.  We rename some parameters at
> > the same time to make it clear that they are referring to spapr global
> > irq numbers.
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> 
> Reviewed-by: Greg Kurz <address@hidden>
> 
> Further cleanup could be to have the XICS backend to only take global
> irq numbers and to convert them to ICS source numbers internally. This
> would put an end to the confusion between srcno/irq in the frontend
> code.

Yeah, maybe.  But the local srcnos do actually make sense from within
the perspective of ICS, so I'm not all that keen to do that.

-- 
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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