[BOOTWRAPPER PATCH 2/2] Add support for GICv5

[Sascha Bischoff]

On Fri, 2026-02-27 at 11:19 +0000, Vladimir Murzin wrote:
> Hi Joey!
> 
> On 2/27/26 11:06, Joey Gouly wrote:
> > Hi!
> > 
> 
> [snip]
> 
> > > +
> > > +static void gic_ppi_init(void) {
> > > +	uint64_t val = 0;
> > > +
> > > +	val |= 1UL << (2 * 31); // Trace Buffer Unit
> > > +	val |= 1UL << (2 * 30); // EL1 Physical Timer
> > > +	val |= 1UL << (2 * 28); // Non-secure EL2 Virtual Timer
> > > +	val |= 1UL << (2 * 27); // EL1 Virtual Timer
> > > +	val |= 1UL << (2 * 26); // Non-secure EL2 Physical Timer
> > > +	val |= 1UL << (2 * 25); // GIC maintenance interrupt
> > > +	val |= 1UL << (2 * 24); // Generic CTI interrupt trigger
> > > event
> > > +	val |= 1UL << (2 * 23); // PMU overflow interrupt
> > > request
> > > +	val |= 1UL << (2 * 22); // Debug communication channel
> > > +	val |= 1UL << (2 * 21); // Profiling Buffer management
> > > interrupt request
> > > +	val |= 1UL << (2 * 15); // Hardware accelerator for
> > > cleaning Dirty state interrupt
> > What about SW_PPI (3) and NS_DB_PPI (2)? Are the left out for a
> > reason?
> > 
> 
> No reason, I just missed them. Thanks for catching that!

Hi both,

I don't fully agree here.

I think that the SW_PPI should be assigned to NS - it is a sane default
so that normal software can use it. There's no pre-defined use case for
this PPI, so it is just used however software chooses to use it. A
potential use case would be for software in the Secure world to poke NS
to say that it has completed some task (FF-A does this sort of thing
using a donated SGI on GICv3, but could use the GICv5 SW_PPI for this
in the future). In this flow, it is assigned to NS, and EL3 makes it
pending as part of the return to NS from S so that NS software receives
the doorbell.

The NS_DB_PPI shouldn't ever be assigned to NS - it is there to alert a
non-NS domain to the fact that NS has pending interrupts. It should
never get signalled when running in NS (NS doesn't need an interrupt to
tell it that it has interrupts ;) ). It is a "Please switch to the NS
domain when you get the opportunity" signal. Hence, the S_DB_PPI,
RL_DB_PPI however should likely be assigned to NS, by default.

The expectation with the DB_PPIs is that EL3 might change their domains
as part of a world-switch. That is, all DB PPIs "belonging" to the non-
target domain would be assigned to the target domain as part of
transitioning via EL3.

A sane default would be to assign the NS_DB_PPI to Secure.

I hope that makes sense.

Sascha

> 
> Cheers
> Vladimir 
>