[PATCH v2 11/36] KVM: arm64: gic-v5: Support GICv5 FGTs & FGUs

[Sascha Bischoff]

On Wed, 2026-01-07 at 11:19 +0000, Jonathan Cameron wrote:
> On Fri, 19 Dec 2025 15:52:39 +0000
> Sascha Bischoff <Sascha.Bischoff at arm.com> wrote:
> 
> > Extend the existing FGT/FGU infrastructure to include the GICv5
> > trap
> > registers (ICH_HFGRTR_EL2, ICH_HFGWTR_EL2, ICH_HFGITR_EL2). This
> > involves mapping the trap registers and their bits to the
> > corresponding feature that introduces them (FEAT_GCIE for all, in
> > this
> > case), and mapping each trap bit to the system register/instruction
> > controlled by it.
> > 
> > As of this change, none of the GICv5 instructions or register
> > accesses
> > are being trapped.
> > 
> > Signed-off-by: Sascha Bischoff <sascha.bischoff at arm.com>
> Hi Sascha,
> 
> Superficial stuff only on code flow to make it easier to extend next
> time.
> 
> Jonathan
> 
> 
> > diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> > index 3845b188551b6..5f57dc07cc482 100644
> > --- a/arch/arm64/kvm/config.c
> > +++ b/arch/arm64/kvm/config.c
> 
> > @@ -1511,11 +1595,19 @@ void kvm_vcpu_load_fgt(struct kvm_vcpu
> > *vcpu)
> >  	__compute_fgt(vcpu, HAFGRTR_EL2);
> >  
> >  	if (!cpus_have_final_cap(ARM64_HAS_FGT2))
> > -		return;
> > +		goto skip_fgt2;
> 
> Nicer to avoid more complex code flow and just make the next
> block an if.
> 
> 	if (cpus_have_final_cap(ARM64_HAS_FGT2)) {
> 		__compute_fgt(vcpu, HFGRTR2_EL2);
> 		__compute_fgt(vcpu, HFGWTR2_EL2);
> 		__compute_fgt(vcpu, HFGITR2_EL2);
> 		__compute_fgt(vcpu, HDFGRTR2_EL2);
> 		__compute_fgt(vcpu, HDFGWTR2_EL2);
> 	}
> >  
> >  	__compute_fgt(vcpu, HFGRTR2_EL2);
> >  	__compute_fgt(vcpu, HFGWTR2_EL2);
> >  	__compute_fgt(vcpu, HFGITR2_EL2);
> >  	__compute_fgt(vcpu, HDFGRTR2_EL2);
> >  	__compute_fgt(vcpu, HDFGWTR2_EL2);
> > +
> > +skip_fgt2:
> > +	if (!cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF))
> Given the above shows this code sometimes gets extended I'd
> be tempted to just go with
> 	if (cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF)) {
> 		__compute_fgt(vcpu, ICH_HFGRTR_EL2);
> 		__compute_fgt(vcpu, ICH_HFGWTR_EL2);
> 		__compute_fgt(vcpu, ICH_HFGITR_EL2);
> 	}
> 
> From the start and avoid future churn or goto nasties.

Yeah, you're probably right. Done.

Thanks,
Sascha

> 
> > 	
> > +		return;
> > +
> > +	__compute_fgt(vcpu, ICH_HFGRTR_EL2);
> > +	__compute_fgt(vcpu, ICH_HFGWTR_EL2);
> > +	__compute_fgt(vcpu, ICH_HFGITR_EL2);
> >  }
> 
> 
>