Re: [PATCH 3/3] KVM: arm64: Limit clearing of ID_{AA64PFR0,PFR1}_EL1.GIC to userspace irqchip

[Oliver Upton <oliver.upton@linux.dev>]

On Mon, Oct 13, 2025 at 09:32:07AM +0100, Marc Zyngier wrote:
> Now that the idreg's GIC field is in sync with the irqchip, limit
> the runtime clearing of these fields to the pathological case where
> we do not have an in-kernel GIC.
> 
> Fixes: 5cb57a1aff755 ("KVM: arm64: Zero ID_AA64PFR0_EL1.GIC when no GICv3 is presented to the guest")
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 73dcefe51a3e7..25cfd0f9541f5 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -5494,9 +5494,7 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu)
>  
>  	guard(mutex)(&kvm->arch.config_lock);
>  
> -	if (!(static_branch_unlikely(&kvm_vgic_global_state.gicv3_cpuif) &&
> -	      irqchip_in_kernel(kvm) &&
> -	      kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)) {
> +	if (!irqchip_in_kernel(kvm)) {
>  		kvm->arch.id_regs[IDREG_IDX(SYS_ID_AA64PFR0_EL1)] &= ~ID_AA64PFR0_EL1_GIC_MASK;
>  		kvm->arch.id_regs[IDREG_IDX(SYS_ID_PFR1_EL1)] &= ~ID_PFR1_EL1_GIC_MASK;

Pre-existing, but converting this to the accessors would be a good idea.

Thanks,
Oliver