Re: [PATCH 08/18] KVM: arm64: vgic: Rationalise per-CPU irq accessor

[Joey Gouly <joey.gouly@arm.com>]

On Wed, Apr 15, 2026 at 12:55:49PM +0100, Marc Zyngier wrote:
> Despite adding the necessary infrastructure to identify irq types,
> vgic_get_vcpu_irq() treats GICv5 PPIs in a special way, which
> impairs the readability of the code.
> 
> Use the existing irq classifiers to handle per-CPU irqs for all
> vgic types, and let the normal control flow reach global interrupt
> handling without any v5-specific path.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/vgic/vgic.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
> index 3ac6d49bc4876..b697678d68b01 100644
> --- a/arch/arm64/kvm/vgic/vgic.c
> +++ b/arch/arm64/kvm/vgic/vgic.c
> @@ -106,24 +106,23 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, u32 intid)
>  
>  struct vgic_irq *vgic_get_vcpu_irq(struct kvm_vcpu *vcpu, u32 intid)
>  {
> +	enum kvm_device_type type;
> +
>  	if (WARN_ON(!vcpu))
>  		return NULL;
>  
> -	if (vgic_is_v5(vcpu->kvm)) {
> -		u32 int_num, hwirq_id;
> -
> -		if (!__irq_is_ppi(KVM_DEV_TYPE_ARM_VGIC_V5, intid))
> -			return NULL;
> -
> -		hwirq_id = FIELD_GET(GICV5_HWIRQ_ID, intid);
> -		int_num = array_index_nospec(hwirq_id, VGIC_V5_NR_PRIVATE_IRQS);
> +	type = vcpu->kvm->arch.vgic.vgic_model;
>  
> -		return &vcpu->arch.vgic_cpu.private_irqs[int_num];
> -	}
> +	if (__irq_is_sgi(type, intid) || __irq_is_ppi(type, intid)) {
> +		switch (type) {
> +		case KVM_DEV_TYPE_ARM_VGIC_V5:
> +			intid = vgic_v5_get_hwirq_id(intid);
> +			intid = array_index_nospec(intid, VGIC_V5_NR_PRIVATE_IRQS);
> +			break;
> +		default:
> +			intid = array_index_nospec(intid, VGIC_NR_PRIVATE_IRQS);
> +		}
>  
> -	/* SGIs and PPIs */
> -	if (intid < VGIC_NR_PRIVATE_IRQS) {
> -		intid = array_index_nospec(intid, VGIC_NR_PRIVATE_IRQS);
>  		return &vcpu->arch.vgic_cpu.private_irqs[intid];
>  	}
>  

It preserves the behaviour of returning NULL for anything other than PPI on
gic-v5, because the fallthrough to vgic_get_irq() returns NULL for gic-v5 and
__irq_is_sgi() is always false for gic-v5.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>

Thanks,
Joey