irqchip/gic-v4.1: Plumb skeletal VPE irqchip

Just like for GICv4.0, each VPE has its own doorbell interrupt, and
thus an irqchip that manages them. Since the doorbell management is
quite different on GICv4.1, let's introduce an almost empty irqchip
the will get populated over the next new patches.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Link: https://lore.kernel.org/r/20191224111055.11836-10-maz@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -3553,6 +3553,32 @@ static struct irq_chip its_vpe_irq_chip = {
 	.irq_set_vcpu_affinity	= its_vpe_set_vcpu_affinity,
 };
 
+static int its_vpe_4_1_set_vcpu_affinity(struct irq_data *d, void *vcpu_info)
+{
+	struct its_cmd_info *info = vcpu_info;
+
+	switch (info->cmd_type) {
+	case SCHEDULE_VPE:
+		return 0;
+
+	case DESCHEDULE_VPE:
+		return 0;
+
+	case INVALL_VPE:
+		return 0;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static struct irq_chip its_vpe_4_1_irq_chip = {
+	.name			= "GICv4.1-vpe",
+	.irq_eoi		= irq_chip_eoi_parent,
+	.irq_set_affinity	= its_vpe_set_affinity,
+	.irq_set_vcpu_affinity	= its_vpe_4_1_set_vcpu_affinity,
+};
+
 static int its_vpe_id_alloc(void)
 {
 	return ida_simple_get(&its_vpeid_ida, 0, ITS_MAX_VPEID, GFP_KERNEL);
@@ -3633,6 +3659,7 @@ static void its_vpe_irq_domain_free(struct irq_domain *domain,
 static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
 				    unsigned int nr_irqs, void *args)
 {
+	struct irq_chip *irqchip = &its_vpe_irq_chip;
 	struct its_vm *vm = args;
 	unsigned long *bitmap;
 	struct page *vprop_page;
@@ -3660,6 +3687,9 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
 	vm->nr_db_lpis = nr_ids;
 	vm->vprop_page = vprop_page;
 
+	if (gic_rdists->has_rvpeid)
+		irqchip = &its_vpe_4_1_irq_chip;
+
 	for (i = 0; i < nr_irqs; i++) {
 		vm->vpes[i]->vpe_db_lpi = base + i;
 		err = its_vpe_init(vm->vpes[i]);
@@ -3670,7 +3700,7 @@ static int its_vpe_irq_domain_alloc(struct irq_domain *domain, unsigned int virq
 		if (err)
 			break;
 		irq_domain_set_hwirq_and_chip(domain, virq + i, i,
-					      &its_vpe_irq_chip, vm->vpes[i]);
+					      irqchip, vm->vpes[i]);
 		set_bit(i, bitmap);
 	}