5 files changed, 38 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f5662b7a34d1..62b6e8067a5b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1536,6 +1536,10 @@ and is between 256 and 4096 characters. It is defined in the file
                                 primary IO-APIC for bridges that cannot disable
                                 boot IRQs. This fixes a source of spurious IRQs
                                 when the system masks IRQs.
+                noioapicreroute [APIC] Disable workaround that uses the
+                                boot IRQ equivalent of an IRQ that connects to
+                                a chipset where boot IRQs cannot be disabled.
+                                The opposite of ioapicreroute.
                 biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
                                 routing table. These calls are known to be buggy
                                 on several machines and they hang the machine
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 96e0c2ebc388..09521332636b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -665,6 +665,30 @@ config X86_VISWS_APIC
         def_bool y
         depends on X86_32 && X86_VISWS
 
+config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
+        bool "Reroute for broken boot IRQs"
+        default n
+        depends on X86_IO_APIC
+        help
+          This option enables a workaround that fixes a source of
+          spurious interrupts. This is recommended when threaded
+          interrupt handling is used on systems where the generation of
+          superfluous "boot interrupts" cannot be disabled.
+
+          Some chipsets generate a legacy INTx "boot IRQ" when the IRQ
+          entry in the chipset's IO-APIC is masked (as, e.g. the RT
+          kernel does during interrupt handling). On chipsets where this
+          boot IRQ generation cannot be disabled, this workaround keeps
+          the original IRQ line masked so that only the equivalent "boot
+          IRQ" is delivered to the CPUs. The workaround also tells the
+          kernel to set up the IRQ handler on the boot IRQ line. In this
+          way only one interrupt is delivered to the kernel. Otherwise
+          the spurious second interrupt may cause the kernel to bring
+          down (vital) interrupt lines.
+
+          Only affects "broken" chipsets. Interrupt sharing may be
+          increased on these systems.
+
 config X86_MCE
         bool "Machine Check Exception"
         depends on !X86_VOYAGER
diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 1485a26ddcef..bb1a01f089e2 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -24,7 +24,11 @@ unsigned int pci_early_dump_regs;
 static int pci_bf_sort;
 int pci_routeirq;
 int noioapicquirk;
+#ifdef CONFIG_X86_REROUTE_FOR_BROKEN_BOOT_IRQS
+int noioapicreroute = 0;
+#else
 int noioapicreroute = 1;
+#endif
 int pcibios_last_bus = -1;
 unsigned long pirq_table_addr;
 struct pci_bus *pci_root_bus;
@@ -528,6 +532,10 @@ char * __devinit  pcibios_setup(char *str)
                 if (noioapicreroute != -1)
                         noioapicreroute = 0;
                 return NULL;
+        } else if (!strcmp(str, "noioapicreroute")) {
+                if (noioapicreroute != -1)
+                        noioapicreroute = 1;
+                return NULL;
         }
         return str;
 }
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 0911b0c60b64..c880dd0bbfb5 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -1397,7 +1397,7 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_INTEL,	0x260b, quirk_intel_pcie_pm);
  */
 static void quirk_reroute_to_boot_interrupts_intel(struct pci_dev *dev)
 {
-        if (noioapicquirk)
+        if (noioapicquirk || noioapicreroute)
                 return;
 
         dev->irq_reroute_variant = INTEL_IRQ_REROUTE_VARIANT;
diff --git a/include/asm-x86/pci.h b/include/asm-x86/pci.h
index 52a29f7668ef..9584d6d5eb93 100644
--- a/include/asm-x86/pci.h
+++ b/include/asm-x86/pci.h
@@ -20,7 +20,7 @@ struct pci_sysdata {
 
 extern int pci_routeirq;
 extern int noioapicquirk;
-extern int ioapicreroute;
+extern int noioapicreroute;
 
 /* scan a bus after allocating a pci_sysdata for it */
 extern struct pci_bus *pci_scan_bus_on_node(int busno, struct pci_ops *ops,