Index: mptbl.c
===================================================================
--- mptbl.c	(revision 265211)
+++ mptbl.c	(working copy)
@@ -51,6 +51,7 @@
 
 #define IOAPIC_PADDR		0xFEC00000
 #define IOAPIC_VERSION		0x11
+#define	IOAPIC_ID		0
 
 #define MP_SPECREV		4
 #define MPFP_SIG		"_MP_"
@@ -77,10 +78,10 @@
 #define	MPEII_NUM_LOCAL_IRQ	2
 
 /* Bus entry defines */
-#define MPE_NUM_BUSES		2
 #define MPE_BUSNAME_LEN		6
 #define MPE_BUSNAME_ISA		"ISA   "
 #define MPE_BUSNAME_PCI		"PCI   "
+static int isa_bus;
 
 static void *oem_tbl_start;
 static int oem_tbl_size;
@@ -165,20 +166,36 @@
 	mpie->dst_apic_int = 1;
 }
 
-static void
+static int
 mpt_build_bus_entries(bus_entry_ptr mpeb)
 {
+	int bus, max_pcibus;
+	bus_entry_ptr mpeb_first;
 
+	mpeb_first = mpeb;
+
+	max_pcibus = -1;
+	for (bus = 0; bus <= PCI_BUSMAX; bus++) {
+		if (pci_bus_configured(bus)) {
+			max_pcibus = bus;
+			memset(mpeb, 0, sizeof(*mpeb));
+			mpeb->type = MPCT_ENTRY_BUS;
+			mpeb->bus_id = bus;
+			memcpy(mpeb->bus_type, MPE_BUSNAME_PCI,
+			    MPE_BUSNAME_LEN);
+			mpeb++;
+		}
+	}
+
+	isa_bus = max_pcibus + 1;
+
 	memset(mpeb, 0, sizeof(*mpeb));
 	mpeb->type = MPCT_ENTRY_BUS;
-	mpeb->bus_id = 0;
-	memcpy(mpeb->bus_type, MPE_BUSNAME_PCI, MPE_BUSNAME_LEN);
+	mpeb->bus_id = isa_bus;
+	memcpy(mpeb->bus_type, MPE_BUSNAME_ISA, MPE_BUSNAME_LEN);
 	mpeb++;
 
-	memset(mpeb, 0, sizeof(*mpeb));
-	mpeb->type = MPCT_ENTRY_BUS;
-	mpeb->bus_id = 1;	
-	memcpy(mpeb->bus_type, MPE_BUSNAME_ISA, MPE_BUSNAME_LEN);
+	return (mpeb - mpeb_first);
 }
 
 static void
@@ -233,7 +250,7 @@
 }
 
 static void
-mpt_build_ioint_entries(int_entry_ptr mpie, int id)
+mpt_build_ioint_entries(int_entry_ptr mpie, int ioapic_id)
 {
 	int pin, bus;
 
@@ -247,12 +264,12 @@
 	for (pin = 0; pin < 16; pin++) {
 		memset(mpie, 0, sizeof(*mpie));
 		mpie->type = MPCT_ENTRY_INT;
-		mpie->src_bus_id = 1;
-		mpie->dst_apic_id = id;
+		mpie->src_bus_id = isa_bus;
+		mpie->dst_apic_id = ioapic_id;
 
 		/*
 		 * All default configs route IRQs from bus 0 to the first 16
-		 * pins of the first I/O APIC with an APIC ID of 2.
+		 * pins of the first I/O APIC.
 		 */
 		mpie->dst_apic_int = pin;
 		switch (pin) {
@@ -303,7 +320,7 @@
 	proc_entry_ptr		mpep;
 	mpfps_t			mpfp;
 	int_entry_ptr		mpie;
-	int			ioints, bus;
+	int			ioints, num_buses;
 	char 			*curraddr;
 	char 			*startaddr;
 
@@ -313,21 +330,6 @@
 		return (ENOMEM);
 	}
 
-	/*
-	 * There is no way to advertise multiple PCI hierarchies via MPtable
-	 * so require that there is no PCI hierarchy with a non-zero bus
-	 * number.
-	 */
-	for (bus = 1; bus <= PCI_BUSMAX; bus++) {
-		if (pci_bus_configured(bus)) {
-			fprintf(stderr, "MPtable is incompatible with "
-			    "multiple PCI hierarchies.\r\n");
-			fprintf(stderr, "MPtable generation can be disabled "
-			    "by passing the -Y option to bhyve(8).\r\n");
-			return (EINVAL);
-		}
-	}
-
 	curraddr = startaddr;
 	mpfp = (mpfps_t)curraddr;
 	mpt_build_mpfp(mpfp, MPTABLE_BASE);
@@ -343,18 +345,18 @@
 	mpch->entry_count += ncpu;
 
 	mpeb = (bus_entry_ptr) curraddr;
-	mpt_build_bus_entries(mpeb);
-	curraddr += sizeof(*mpeb) * MPE_NUM_BUSES;
-	mpch->entry_count += MPE_NUM_BUSES;
+	num_buses = mpt_build_bus_entries(mpeb);
+	curraddr += sizeof(*mpeb) * num_buses;
+	mpch->entry_count += num_buses;
 
 	mpei = (io_apic_entry_ptr)curraddr;
-	mpt_build_ioapic_entries(mpei, 0);
+	mpt_build_ioapic_entries(mpei, IOAPIC_ID);
 	curraddr += sizeof(*mpei);
 	mpch->entry_count++;
 
 	mpie = (int_entry_ptr) curraddr;
 	ioints = mpt_count_ioint_entries();
-	mpt_build_ioint_entries(mpie, 0);
+	mpt_build_ioint_entries(mpie, IOAPIC_ID);
 	curraddr += sizeof(*mpie) * ioints;
 	mpch->entry_count += ioints;