x86/irq: Initialize PCI/MSI domain at PCI init time

No point in initializing the default PCI/MSI interrupt domain early and no
point to create it when XEN PV/HVM/DOM0 are active.

Move the initialization to pci_arch_init() and convert it to init ops so
that XEN can override it as XEN has it's own PCI/MSI management. The XEN
override comes in a later step.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200826112332.859209894@linutronix.de

arch/x86/include/asm/irqdomain.h

@@ -51,9 +51,11 @@ extern int mp_irqdomain_ioapic_idx(struct irq_domain *domain);
 #endif /* CONFIG_X86_IO_APIC */
 
 #ifdef CONFIG_PCI_MSI
-extern void arch_init_msi_domain(struct irq_domain *domain);
+void x86_create_pci_msi_domain(void);
+struct irq_domain *native_create_pci_msi_domain(void);
 #else
-static inline void arch_init_msi_domain(struct irq_domain *domain) { }
+static inline void x86_create_pci_msi_domain(void) { }
+#define native_create_pci_msi_domain	NULL
 #endif
 
 #endif

arch/x86/include/asm/x86_init.h

@@ -8,6 +8,7 @@ struct mpc_bus;
 struct mpc_cpu;
 struct mpc_table;
 struct cpuinfo_x86;
+struct irq_domain;
 
 /**
  * struct x86_init_mpparse - platform specific mpparse ops
@@ -42,12 +43,14 @@ struct x86_init_resources {
  * @intr_init:			interrupt init code
  * @intr_mode_select:		interrupt delivery mode selection
  * @intr_mode_init:		interrupt delivery mode setup
+ * @create_pci_msi_domain:	Create the PCI/MSI interrupt domain
  */
 struct x86_init_irqs {
 	void (*pre_vector_init)(void);
 	void (*intr_init)(void);
 	void (*intr_mode_select)(void);
 	void (*intr_mode_init)(void);
+	struct irq_domain *(*create_pci_msi_domain)(void);
 };
 
 /**

arch/x86/kernel/apic/msi.c

@@ -21,7 +21,7 @@
 #include <asm/apic.h>
 #include <asm/irq_remapping.h>
 
-static struct irq_domain *msi_default_domain;
+static struct irq_domain *x86_pci_msi_default_domain __ro_after_init;
 
 static void __irq_msi_compose_msg(struct irq_cfg *cfg, struct msi_msg *msg)
 {
@@ -191,7 +191,7 @@ int native_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 
 	domain = irq_remapping_get_irq_domain(&info);
 	if (domain == NULL)
-		domain = msi_default_domain;
+		domain = x86_pci_msi_default_domain;
 	if (domain == NULL)
 		return -ENOSYS;
 
@@ -234,25 +234,32 @@ static struct msi_domain_info pci_msi_domain_info = {
 	.handler_name	= "edge",
 };
 
-void __init arch_init_msi_domain(struct irq_domain *parent)
+struct irq_domain * __init native_create_pci_msi_domain(void)
 {
 	struct fwnode_handle *fn;
+	struct irq_domain *d;
 
 	if (disable_apic)
-		return;
+		return NULL;
 
 	fn = irq_domain_alloc_named_fwnode("PCI-MSI");
-	if (fn) {
-		msi_default_domain =
-			pci_msi_create_irq_domain(fn, &pci_msi_domain_info,
-						  parent);
-	}
-	if (!msi_default_domain) {
+	if (!fn)
+		return NULL;
+
+	d = pci_msi_create_irq_domain(fn, &pci_msi_domain_info,
+				      x86_vector_domain);
+	if (!d) {
 		irq_domain_free_fwnode(fn);
-		pr_warn("failed to initialize irqdomain for MSI/MSI-x.\n");
+		pr_warn("Failed to initialize PCI-MSI irqdomain.\n");
 	} else {
-		msi_default_domain->flags |= IRQ_DOMAIN_MSI_NOMASK_QUIRK;
+		d->flags |= IRQ_DOMAIN_MSI_NOMASK_QUIRK;
 	}
+	return d;
+}
+
+void __init x86_create_pci_msi_domain(void)
+{
+	x86_pci_msi_default_domain = x86_init.irqs.create_pci_msi_domain();
 }
 
 #ifdef CONFIG_IRQ_REMAP

arch/x86/kernel/apic/vector.c

@@ -714,8 +714,6 @@ int __init arch_early_irq_init(void)
 	BUG_ON(x86_vector_domain == NULL);
 	irq_set_default_host(x86_vector_domain);
 
-	arch_init_msi_domain(x86_vector_domain);
-
 	BUG_ON(!alloc_cpumask_var(&vector_searchmask, GFP_KERNEL));
 
 	/*

arch/x86/kernel/x86_init.c

@@ -24,6 +24,7 @@
 #include <asm/tsc.h>
 #include <asm/iommu.h>
 #include <asm/mach_traps.h>
+#include <asm/irqdomain.h>
 
 void x86_init_noop(void) { }
 void __init x86_init_uint_noop(unsigned int unused) { }
@@ -76,7 +77,8 @@ struct x86_init_ops x86_init __initdata = {
 		.pre_vector_init	= init_ISA_irqs,
 		.intr_init		= native_init_IRQ,
 		.intr_mode_select	= apic_intr_mode_select,
-		.intr_mode_init		= apic_intr_mode_init
+		.intr_mode_init		= apic_intr_mode_init,
+		.create_pci_msi_domain	= native_create_pci_msi_domain,
 	},
 
 	.oem = {

arch/x86/pci/init.c

@@ -3,6 +3,7 @@
 #include <linux/init.h>
 #include <asm/pci_x86.h>
 #include <asm/x86_init.h>
+#include <asm/irqdomain.h>
 
 /* arch_initcall has too random ordering, so call the initializers
    in the right sequence from here. */
@@ -10,6 +11,8 @@ static __init int pci_arch_init(void)
 {
 	int type;
 
+	x86_create_pci_msi_domain();
+
 	type = pci_direct_probe();
 
 	if (!(pci_probe & PCI_PROBE_NOEARLY))