2 files changed, 16 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index 77b4c608cca0..0de3ea938830 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -1777,6 +1777,8 @@ static inline void unlock_ExtINT_logic(void)
         spin_unlock_irqrestore(&ioapic_lock, flags);
 }
 
+int timer_uses_ioapic_pin_0;
+
 /*
  * This code may look a bit paranoid, but it's supposed to cooperate with
  * a wide range of boards and BIOS bugs.  Fortunately only the timer IRQ
@@ -1814,6 +1816,9 @@ static inline void check_timer(void)
         pin2  = ioapic_i8259.pin;
         apic2 = ioapic_i8259.apic;
 
+        if (pin1 == 0)
+                timer_uses_ioapic_pin_0 = 1;
+
         apic_printk(APIC_VERBOSE,KERN_INFO "..TIMER: vector=0x%02X apic1=%d pin1=%d apic2=%d pin2=%d\n",
                 vector, apic1, pin1, apic2, pin2);
 
diff --git a/arch/x86_64/kernel/mpparse.c b/arch/x86_64/kernel/mpparse.c
index b17cf3eba359..083da7e606b1 100644
--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -968,7 +968,17 @@ int mp_register_gsi(u32 gsi, int triggering, int polarity)
                  */
                 int irq = gsi;
                 if (gsi < MAX_GSI_NUM) {
-                        if (gsi > 15)
+                        /*
+                         * Retain the VIA chipset work-around (gsi > 15), but
+                         * avoid a problem where the 8254 timer (IRQ0) is setup
+                         * via an override (so it's not on pin 0 of the ioapic),
+                         * and at the same time, the pin 0 interrupt is a PCI
+                         * type.  The gsi > 15 test could cause these two pins
+                         * to be shared as IRQ0, and they are not shareable.
+                         * So test for this condition, and if necessary, avoid
+                         * the pin collision.
+                         */
+                        if (gsi > 15 || (gsi == 0 && !timer_uses_ioapic_pin_0))
                                 gsi = pci_irq++;
                         /*
                          * Don't assign IRQ used by ACPI SCI