xen/pci: Move check for acpi_sci_override_gsi to xen_setup_acpi_sci.

Previously we would check for acpi_sci_override_gsi == gsi every time
a PCI device was enabled. That works during early bootup, but later
on it could lead to triggering unnecessarily the acpi_gsi_to_irq(..) lookup.
The reason is that acpi_sci_override_gsi was declared in __initdata and
after early bootup could contain bogus values.

This patch moves the check for acpi_sci_override_gsi to the
site where the ACPI SCI is preset.

CC: stable@kernel.org
Reported-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
Tested-by: Raghavendra D Prabhu <rprabhu@wnohang.net>
[http://lists.xensource.com/archives/html/xen-devel/2011-07/msg00154.html]
Suggested-by:  Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 28 insertions, 28 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index fe008309ffec..f567965c0620 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -327,13 +327,12 @@ int __init pci_xen_hvm_init(void)
 }
 
 #ifdef CONFIG_XEN_DOM0
-static int xen_register_pirq(u32 gsi, int triggering)
+static int xen_register_pirq(u32 gsi, int gsi_override, int triggering)
 {
         int rc, pirq, irq = -1;
         struct physdev_map_pirq map_irq;
         int shareable = 0;
         char *name;
-        bool gsi_override = false;
 
         if (!xen_pv_domain())
                 return -1;
@@ -345,31 +344,12 @@ static int xen_register_pirq(u32 gsi, int triggering)
                 shareable = 1;
                 name = "ioapic-level";
         }
-
         pirq = xen_allocate_pirq_gsi(gsi);
         if (pirq < 0)
                 goto out;
 
-        /* Before we bind the GSI to a Linux IRQ, check whether
-         * we need to override it with bus_irq (IRQ) value. Usually for
-         * IRQs below IRQ_LEGACY_IRQ this holds IRQ == GSI, as so:
-         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 low level)
-         * but there are oddballs where the IRQ != GSI:
-         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 20 low level)
-         * which ends up being: gsi_to_irq[9] == 20
-         * (which is what acpi_gsi_to_irq ends up calling when starting the
-         * the ACPI interpreter and keels over since IRQ 9 has not been
-         * setup as we had setup IRQ 20 for it).
-         */
-        if (gsi == acpi_sci_override_gsi) {
-                /* Check whether the GSI != IRQ */
-                acpi_gsi_to_irq(gsi, &irq);
-                if (irq != gsi)
-                        /* Bugger, we MUST have that IRQ. */
-                        gsi_override = true;
-        }
-        if (gsi_override)
-                irq = xen_bind_pirq_gsi_to_irq(irq, pirq, shareable, name);
+        if (gsi_override >= 0)
+                irq = xen_bind_pirq_gsi_to_irq(gsi_override, pirq, shareable, name);
         else
                 irq = xen_bind_pirq_gsi_to_irq(gsi, pirq, shareable, name);
         if (irq < 0)
@@ -392,7 +372,7 @@ out:
         return irq;
 }
 
-static int xen_register_gsi(u32 gsi, int triggering, int polarity)
+static int xen_register_gsi(u32 gsi, int gsi_override, int triggering, int polarity)
 {
         int rc, irq;
         struct physdev_setup_gsi setup_gsi;
@@ -403,7 +383,7 @@ static int xen_register_gsi(u32 gsi, int triggering, int polarity)
         printk(KERN_DEBUG "xen: registering gsi %u triggering %d polarity %d\n",
                         gsi, triggering, polarity);
 
-        irq = xen_register_pirq(gsi, triggering);
+        irq = xen_register_pirq(gsi, gsi_override, triggering);
 
         setup_gsi.gsi = gsi;
         setup_gsi.triggering = (triggering == ACPI_EDGE_SENSITIVE ? 0 : 1);
@@ -425,6 +405,8 @@ static __init void xen_setup_acpi_sci(void)
         int rc;
         int trigger, polarity;
         int gsi = acpi_sci_override_gsi;
+        int irq = -1;
+        int gsi_override = -1;
 
         if (!gsi)
                 return;
@@ -441,7 +423,25 @@ static __init void xen_setup_acpi_sci(void)
         printk(KERN_INFO "xen: sci override: global_irq=%d trigger=%d "
                         "polarity=%d\n", gsi, trigger, polarity);
 
-        gsi = xen_register_gsi(gsi, trigger, polarity);
+        /* Before we bind the GSI to a Linux IRQ, check whether
+         * we need to override it with bus_irq (IRQ) value. Usually for
+         * IRQs below IRQ_LEGACY_IRQ this holds IRQ == GSI, as so:
+         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 low level)
+         * but there are oddballs where the IRQ != GSI:
+         *  ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 20 low level)
+         * which ends up being: gsi_to_irq[9] == 20
+         * (which is what acpi_gsi_to_irq ends up calling when starting the
+         * the ACPI interpreter and keels over since IRQ 9 has not been
+         * setup as we had setup IRQ 20 for it).
+         */
+        /* Check whether the GSI != IRQ */
+        if (acpi_gsi_to_irq(gsi, &irq) == 0) {
+                if (irq >= 0 && irq != gsi)
+                        /* Bugger, we MUST have that IRQ. */
+                        gsi_override = irq;
+        }
+
+        gsi = xen_register_gsi(gsi, gsi_override, trigger, polarity);
         printk(KERN_INFO "xen: acpi sci %d\n", gsi);
 
         return;
@@ -450,7 +450,7 @@ static __init void xen_setup_acpi_sci(void)
 static int acpi_register_gsi_xen(struct device *dev, u32 gsi,
                                  int trigger, int polarity)
 {
-        return xen_register_gsi(gsi, trigger, polarity);
+        return xen_register_gsi(gsi, -1 /* no GSI override */, trigger, polarity);
 }
 
 static int __init pci_xen_initial_domain(void)
@@ -489,7 +489,7 @@ void __init xen_setup_pirqs(void)
                 if (acpi_get_override_irq(irq, &trigger, &polarity) == -1)
                         continue;
 
-                xen_register_pirq(irq,
+                xen_register_pirq(irq, -1 /* no GSI override */,
                         trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE);
         }
 }