KVM: arm64: Restore GICv2-on-GICv3 functionality

When reworking the vgic locking, the vgic distributor registration
got simplified, which was a very good cleanup. But just a tad too
radical, as we now register the *native* vgic only, ignoring the
GICv2-on-GICv3 that allows pre-historic VMs (or so I thought)
to run.

As it turns out, QEMU still defaults to GICv2 in some cases, and
this breaks Nathan's setup!

Fix it by propagating the *requested* vgic type rather than the
host's version.

Fixes: 59112e9 ("KVM: arm64: vgic: Fix a circular locking issue")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
link: https://lore.kernel.org/r/20230606221525.GA2269598@dev-arch.thelio-3990X

arch/arm64/kvm/vgic/vgic-init.c

@@ -446,6 +446,7 @@ int vgic_lazy_init(struct kvm *kvm)
 int kvm_vgic_map_resources(struct kvm *kvm)
 {
 	struct vgic_dist *dist = &kvm->arch.vgic;
+	enum vgic_type type;
 	gpa_t dist_base;
 	int ret = 0;
 
@@ -460,10 +461,13 @@ int kvm_vgic_map_resources(struct kvm *kvm)
 	if (!irqchip_in_kernel(kvm))
 		goto out;
 
-	if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2)
+	if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V2) {
 		ret = vgic_v2_map_resources(kvm);
-	else
+		type = VGIC_V2;
+	} else {
 		ret = vgic_v3_map_resources(kvm);
+		type = VGIC_V3;
+	}
 
 	if (ret) {
 		__kvm_vgic_destroy(kvm);
@@ -473,8 +477,7 @@ int kvm_vgic_map_resources(struct kvm *kvm)
 	dist_base = dist->vgic_dist_base;
 	mutex_unlock(&kvm->arch.config_lock);
 
-	ret = vgic_register_dist_iodev(kvm, dist_base,
-				       kvm_vgic_global_state.type);
+	ret = vgic_register_dist_iodev(kvm, dist_base, type);
 	if (ret) {
 		kvm_err("Unable to register VGIC dist MMIO regions\n");
 		kvm_vgic_destroy(kvm);