KVM: arm64: Let GICv3 save/restore honor visibility attribute

The GICv3 save/restore code never needed any visibility attribute,
but that's about to change. Make vgic_v3_has_cpu_sysregs_attr()
check the visibility in case a register is hidden.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250714122634.3334816-6-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: Marc Zyngier

arch/arm64/kvm/vgic-sys-reg-v3.c

@@ -341,8 +341,12 @@ static u64 attr_to_id(u64 attr)
 
 int vgic_v3_has_cpu_sysregs_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 {
-	if (get_reg_by_id(attr_to_id(attr->attr), gic_v3_icc_reg_descs,
-			  ARRAY_SIZE(gic_v3_icc_reg_descs)))
+	const struct sys_reg_desc *r;
+
+	r = get_reg_by_id(attr_to_id(attr->attr), gic_v3_icc_reg_descs,
+			  ARRAY_SIZE(gic_v3_icc_reg_descs));
+
+	if (r && !sysreg_hidden(vcpu, r))
 		return 0;
 
 	return -ENXIO;