--- linux/arch/i386/kernel/io_apic.c.orig	Tue May 29 12:13:15 2001
+++ linux/arch/i386/kernel/io_apic.c	Tue May 29 12:19:55 2001
@@ -256,10 +256,16 @@
  */
 static int pin_2_irq(int idx, int apic, int pin);
 
-int IO_APIC_get_PCI_irq_vector(int bus, int slot, int pci_pin)
+int IO_APIC_get_PCI_irq_vector(int bus, int slot, int pin)
 {
 	int apic, i, best_guess = -1;
 
+	Dprintk("querying PCI -> IRQ mapping bus:%d, slot:%d, pin:%d.\n",
+		bus, slot, pin);
+	if (mp_bus_id_to_pci_bus[bus] == -1) {
+		printk(KERN_WARNING "PCI BIOS passed nonexistent PCI bus %d!\n", bus);
+		return -1;
+	}
 	for (i = 0; i < mp_irq_entries; i++) {
 		int lbus = mp_irqs[i].mpc_srcbus;
 
@@ -270,14 +276,14 @@
 
 		if ((mp_bus_id_to_type[lbus] == MP_BUS_PCI) &&
 		    !mp_irqs[i].mpc_irqtype &&
-		    (bus == mp_bus_id_to_pci_bus[mp_irqs[i].mpc_srcbus]) &&
+		    (bus == lbus) &&
 		    (slot == ((mp_irqs[i].mpc_srcbusirq >> 2) & 0x1f))) {
 			int irq = pin_2_irq(i,apic,mp_irqs[i].mpc_dstirq);
 
 			if (!(apic || IO_APIC_IRQ(irq)))
 				continue;
 
-			if (pci_pin == (mp_irqs[i].mpc_srcbusirq & 3))
+			if (pin == (mp_irqs[i].mpc_srcbusirq & 3))
 				return irq;
 			/*
 			 * Use the first all-but-pin matching entry as a
@@ -738,9 +744,11 @@
 	printk(KERN_DEBUG ".... register #01: %08X\n", *(int *)&reg_01);
 	printk(KERN_DEBUG ".......     : max redirection entries: %04X\n", reg_01.entries);
 	if (	(reg_01.entries != 0x0f) && /* older (Neptune) boards */
+		(reg_01.entries != 0x11) &&
 		(reg_01.entries != 0x17) && /* typical ISA+PCI boards */
 		(reg_01.entries != 0x1b) && /* Compaq Proliant boards */
 		(reg_01.entries != 0x1f) && /* dual Xeon boards */
+		(reg_01.entries != 0x20) &&
 		(reg_01.entries != 0x22) && /* bigger Xeon boards */
 		(reg_01.entries != 0x2E) &&
 		(reg_01.entries != 0x3F)
--- linux/arch/i386/kernel/mpparse.c.orig	Tue May 29 12:13:15 2001
+++ linux/arch/i386/kernel/mpparse.c	Tue May 29 12:13:46 2001
@@ -36,7 +36,7 @@
  */
 int apic_version [MAX_APICS];
 int mp_bus_id_to_type [MAX_MP_BUSSES];
-int mp_bus_id_to_pci_bus [MAX_MP_BUSSES] = { -1, };
+int mp_bus_id_to_pci_bus [MAX_MP_BUSSES] = { [0 ... MAX_MP_BUSSES-1] = -1 };
 int mp_current_pci_id;
 
 /* I/O APIC entries */
--- linux/arch/i386/kernel/pci-irq.c.orig	Tue May 29 12:13:15 2001
+++ linux/arch/i386/kernel/pci-irq.c	Tue May 29 12:13:46 2001
@@ -660,10 +660,12 @@
 			if (pin) {
 				pin--;		/* interrupt pins are numbered starting from 1 */
 				irq = IO_APIC_get_PCI_irq_vector(dev->bus->number, PCI_SLOT(dev->devfn), pin);
-/*
- * Will be removed completely if things work out well with fuzzy parsing
- */
-#if 0
+	/*
+	 * Busses behind bridges are typically not listed in the MP-table.
+	 * In this case we have to look up the IRQ based on the parent bus,
+	 * parent slot, and pin number. The SMP code detects such bridged
+	 * busses itself so we should get into this branch reliably.
+	 */
 				if (irq < 0 && dev->bus->parent) { /* go back to the bridge */
 					struct pci_dev * bridge = dev->bus->self;
 
@@ -674,7 +676,6 @@
 						printk(KERN_WARNING "PCI: using PPB(B%d,I%d,P%d) to get irq %d\n", 
 							bridge->bus->number, PCI_SLOT(bridge->devfn), pin, irq);
 				}
-#endif
 				if (irq >= 0) {
 					printk(KERN_INFO "PCI->APIC IRQ transform: (B%d,I%d,P%d) -> %d\n",
 						dev->bus->number, PCI_SLOT(dev->devfn), pin, irq);