Re: [XEN PATCH v1 4/5] xen/arm: allow dynamically assigned SGI handlers

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi Michal,

On Wed, Apr 10, 2024 at 3:24 PM Michal Orzel <michal.orzel@xxxxxxx> wrote:
>
> Hi Jens,
>
> On 09/04/2024 17:36, Jens Wiklander wrote:
> >
> >
> > Updates so request_irq() can be used with a dynamically assigned SGI irq
> > as input.
> At this point it would be handy to mention the use case for which you need to 
> add this support

OK, I'll add something like:
This prepares for a later patch where an FF-A schedule receiver
interrupt handler is installed for an SGI generated by the secure
world.

>
> >
> > gic_route_irq_to_xen() don't gic_set_irq_type() for SGIs since they have
> > their type assigned earlier during boot
> Could you elaborate more on that? Do you mean that SGIs are always edge 
> triggered and there's no need
> for setting the type?

Yes, see https://developer.arm.com/documentation/ihi0069/h
4.4 Software Generated Interrupts
SGIs are typically used for inter-processor communication, and are
generated by a write to an SGI register in the
GIC. SGIs can be either Group 0 or Group 1 interrupts, and they can
support only edge-triggered behavior.

How about:
SGI should only be configured as edge triggered.

Thanks,
Jens

>
> >
> > gic_interrupt() is updated to route the dynamically assigned SGIs to
> > do_IRQ() instead of do_sgi(). The latter still handles the statically
> > assigned SGI handlers like for instance GIC_SGI_CALL_FUNCTION.
> >
> > Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> Other than that, it LGTM:
> Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
>
> but I would like other maintainers (especially Julien) to cross check it.
>
> ~Michal