x86/pci: Create PCI/MSI irqdomain after x86_init.pci.arch_init()

Invoking x86_init.irqs.create_pci_msi_domain() before
x86_init.pci.arch_init() breaks XEN PV.

The XEN_PV specific pci.arch_init() function overrides the default
create_pci_msi_domain() which is obviously too late.

As a consequence the XEN PV PCI/MSI allocation goes through the native
path which runs out of vectors and causes malfunction.

Invoke it after x86_init.pci.arch_init().

Fixes: 6b15ffa07dc3 ("x86/irq: Initialize PCI/MSI domain at PCI init time")
Reported-by: Juergen Gross <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: Juergen Gross <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/pci/init.c

···
    in the right sequence from here. */
 static __init int pci_arch_init(void)
 {
-	int type;
-
-	x86_create_pci_msi_domain();
+	int type, pcbios = 1;
 
 	type = pci_direct_probe();
 
 	if (!(pci_probe & PCI_PROBE_NOEARLY))
 		pci_mmcfg_early_init();
 
-	if (x86_init.pci.arch_init && !x86_init.pci.arch_init())
+	if (x86_init.pci.arch_init)
+		pcbios = x86_init.pci.arch_init();
+
+	/*
+	 * Must happen after x86_init.pci.arch_init(). Xen sets up the
+	 * x86_init.irqs.create_pci_msi_domain there.
+	 */
+	x86_create_pci_msi_domain();
+
+	if (!pcbios)
 		return 0;
 
 	pci_pcbios_init();