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

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi Michal,

On Thu, Apr 11, 2024 at 8:44 AM Michal Orzel <michal.orzel@xxxxxxx> wrote:
>
> Hi Jens,
>
> On 11/04/2024 08:12, Jens Wiklander wrote:
> >
> >
> > 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.
> ok
>
> >
> >>
> >>>
> >>> 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.
> Exactly. But you wrote "have their type assigned earlier during boot" which 
> is not true.
> There is no write to ICFGR0 in Xen codebase. They are implicitly edge 
> triggered.
> So I would write:
> "... for SGIs since they are always edge triggered"

I'll use that instead.

Thanks,
Jens

>
> ~Michal