Re: [RFC XEN PATCH v3 2/3] x86/pvh: Add (un)map_pirq and setup_gsi for PVH dom0

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Dec 15, 2023 at 09:24:22AM +0100, Jan Beulich wrote:
> On 14.12.2023 23:49, Stefano Stabellini wrote:
> > On Thu, 14 Dec 2023, Roger Pau Monné wrote:
> >> On Thu, Dec 14, 2023 at 10:58:24AM +0100, Jan Beulich wrote:
> >>> On 14.12.2023 10:55, Roger Pau Monné wrote:
> >>>> One way to bodge this would be to detect whether the caller of
> >>>> XEN_DOMCTL_irq_permission is a PV or an HVM domain, and in case of HVM
> >>>> assume the pirq field is a GSI.  I'm unsure however how that will work
> >>>> with non-x86 architectures.
> > 
> > PIRQ is an x86-only concept. We have event channels but no PIRQs on ARM.
> > I expect RISC-V will be the same.
> > 
> > 
> >>>> It would  be better to introduce a new XEN_DOMCTL_gsi_permission, or
> > 
> > "GSI" is another x86-only concept.
> 
> Just to mention it - going through the ACPI spec, this looks to be an
> arch-neutral ACPI term. It is also used in places which to me look
> pretty Arm-centric.

Oh, indeed, they have retrofitted GSI(V?) for Arm also, as a way to have a
"flat" uniform interrupt space.  So I guess Arm would also need the
GSI type, unless the translation from GSI to SPI or whatever platform
interrupt type is done by the guest and Xen is completely agnostic to
GSIs (if that's even possible).

Thanks, Roger.