Re: [Xen-devel] [PATCH for-4.6 3/4] xen/arm: vgic: notice if the vIRQ is not allocated when the guest enable it

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2015-01-15 at 13:27 +0000, Julien Grall wrote:
> Hi Ian,
> 
> On 14/01/15 12:42, Julien Grall wrote:
> > On 14/01/15 12:28, Ian Campbell wrote:
> >> On Tue, 2015-01-13 at 20:33 +0000, Julien Grall wrote:
> >>> On 13/01/15 15:55, Ian Campbell wrote:
> >>>> On Fri, 2014-12-12 at 14:43 +0000, Julien Grall wrote:
> >>>>> This help for guest interrupts debugging. If the vIRQ is not allocate,
> >>>>> this means that nothing is wired to it.
> >>>>
> >>>> Should we short circuit the rest of the enable operation for this IRQ
> >>>> then? i.e. implement such writes as ignored, e.g. not reflect it in
> >>>> reads of ISENABLER etc.
> >>>>
> >>>> What (if anything) does the GIC spec have to say on the subject?
> >>>
> >>> "A register bit corresponding to an unimplemented interrupt is RAZ/WI."
> >>>
> >>> The goal of this print was mostly for debugging physical IRQ routed to a
> >>> guest.
> >>>
> >>> I could extend to ignore write to any register that should be RAZ/WI for
> >>> this specific interrupt.
> >>
> >> Since those are the defined semantics I think that is the best thing to
> >> do.
> > 
> > Ok. I will look at it to see how we can implement it.
> 
> So I looked to the code. It may need some rework to effectively
> implement most of registers bits RAZ/WI when the interrupt doesn't exist.
> 
> As this series is required for the ACPI series, I suggest to defer this
> work in a follow-up series.

OK.



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