linux-kernel - [PATCH] x86/pci: Create PCI/MSI irqdomain after x86_init.pci.arch

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Date:   Wed, 10 Feb 2021 16:27:41 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Juergen Gross <jgross@...e.com>, x86@...nel.org,
        Bjorn Helgaas <helgaas@...nel.org>,
        xen-devel@...ts.xenproject.org
Subject: [PATCH] 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 <jgross@...e.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Juergen Gross <jgross@...e.com>
Cc: stable@...r.kernel.org
---
 arch/x86/pci/init.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

--- a/arch/x86/pci/init.c
+++ b/arch/x86/pci/init.c
@@ -9,16 +9,23 @@
    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();