diff --git a/hw/spapr_pci.c b/hw/spapr_pci.c
index a564c007b4..25b400aa47 100644
--- a/hw/spapr_pci.c
+++ b/hw/spapr_pci.c
@@ -198,16 +198,20 @@ static void rtas_write_pci_config(sPAPREnvironment *spapr,
     finish_write_pci_config(spapr, 0, addr, size, val, rets);
 }
 
+static int pci_spapr_swizzle(int slot, int pin)
+{
+    return (slot + pin) % PCI_NUM_PINS;
+}
+
 static int pci_spapr_map_irq(PCIDevice *pci_dev, int irq_num)
 {
     /*
      * Here we need to convert pci_dev + irq_num to some unique value
-     * which is less than number of IRQs on the specific bus (now it
-     * is 16).  At the moment irq_num == device_id (number of the
-     * slot?)
-     * FIXME: we should swizzle in fn and irq_num
+     * which is less than number of IRQs on the specific bus (4).  We
+     * use standard PCI swizzling, that is (slot number + pin number)
+     * % 4.
      */
-    return (pci_dev->devfn >> 3) % SPAPR_PCI_NUM_LSI;
+    return pci_spapr_swizzle(PCI_SLOT(pci_dev->devfn), irq_num);
 }
 
 static void pci_spapr_set_irq(void *opaque, int irq_num, int level)
@@ -304,13 +308,13 @@ static int spapr_phb_init(SysBusDevice *s)
                            phb->busname ? phb->busname : phb->dtbusname,
                            pci_spapr_set_irq, pci_spapr_map_irq, phb,
                            &phb->memspace, &phb->iospace,
-                           PCI_DEVFN(0, 0), SPAPR_PCI_NUM_LSI);
+                           PCI_DEVFN(0, 0), PCI_NUM_PINS);
     phb->host_state.bus = bus;
 
     QLIST_INSERT_HEAD(&spapr->phbs, phb, list);
 
     /* Initialize the LSI table */
-    for (i = 0; i < SPAPR_PCI_NUM_LSI; i++) {
+    for (i = 0; i < PCI_NUM_PINS; i++) {
         qemu_irq qirq;
         uint32_t num;
 
@@ -392,8 +396,7 @@ int spapr_populate_pci_devices(sPAPRPHBState *phb,
                                uint32_t xics_phandle,
                                void *fdt)
 {
-    PCIBus *bus = phb->host_state.bus;
-    int bus_off, i;
+    int bus_off, i, j;
     char nodename[256];
     uint32_t bus_range[] = { cpu_to_be32(0), cpu_to_be32(0xff) };
     struct {
@@ -415,8 +418,8 @@ int spapr_populate_pci_devices(sPAPRPHBState *phb,
     };
     uint64_t bus_reg[] = { cpu_to_be64(phb->buid), 0 };
     uint32_t interrupt_map_mask[] = {
-        cpu_to_be32(b_ddddd(-1)|b_fff(0)), 0x0, 0x0, 0x0};
-    uint32_t interrupt_map[bus->nirq][7];
+        cpu_to_be32(b_ddddd(-1)|b_fff(0)), 0x0, 0x0, cpu_to_be32(-1)};
+    uint32_t interrupt_map[PCI_SLOT_MAX * PCI_NUM_PINS][7];
 
     /* Start populating the FDT */
     sprintf(nodename, "pci@%" PRIx64, phb->buid);
@@ -450,19 +453,23 @@ int spapr_populate_pci_devices(sPAPRPHBState *phb,
      */
     _FDT(fdt_setprop(fdt, bus_off, "interrupt-map-mask",
                      &interrupt_map_mask, sizeof(interrupt_map_mask)));
-    for (i = 0; i < 7; i++) {
-        uint32_t *irqmap = interrupt_map[i];
-        irqmap[0] = cpu_to_be32(b_ddddd(i)|b_fff(0));
-        irqmap[1] = 0;
-        irqmap[2] = 0;
-        irqmap[3] = 0;
-        irqmap[4] = cpu_to_be32(xics_phandle);
-        irqmap[5] = cpu_to_be32(phb->lsi_table[i % SPAPR_PCI_NUM_LSI].dt_irq);
-        irqmap[6] = cpu_to_be32(0x8);
+    for (i = 0; i < PCI_SLOT_MAX; i++) {
+        for (j = 0; j < PCI_NUM_PINS; j++) {
+            uint32_t *irqmap = interrupt_map[i*PCI_NUM_PINS + j];
+            int lsi_num = pci_spapr_swizzle(i, j);
+
+            irqmap[0] = cpu_to_be32(b_ddddd(i)|b_fff(0));
+            irqmap[1] = 0;
+            irqmap[2] = 0;
+            irqmap[3] = cpu_to_be32(j+1);
+            irqmap[4] = cpu_to_be32(xics_phandle);
+            irqmap[5] = cpu_to_be32(phb->lsi_table[lsi_num].dt_irq);
+            irqmap[6] = cpu_to_be32(0x8);
+        }
     }
     /* Write interrupt map */
     _FDT(fdt_setprop(fdt, bus_off, "interrupt-map", &interrupt_map,
-                     7 * sizeof(interrupt_map[0])));
+                     sizeof(interrupt_map)));
 
     return 0;
 }
diff --git a/hw/spapr_pci.h b/hw/spapr_pci.h
index 039f85bd4b..f54c2e8108 100644
--- a/hw/spapr_pci.h
+++ b/hw/spapr_pci.h
@@ -23,11 +23,10 @@
 #if !defined(__HW_SPAPR_PCI_H__)
 #define __HW_SPAPR_PCI_H__
 
+#include "hw/pci.h"
 #include "hw/pci_host.h"
 #include "hw/xics.h"
 
-#define SPAPR_PCI_NUM_LSI   16
-
 typedef struct sPAPRPHBState {
     SysBusDevice busdev;
     PCIHostState host_state;
@@ -43,7 +42,7 @@ typedef struct sPAPRPHBState {
     struct {
         uint32_t dt_irq;
         qemu_irq qirq;
-    } lsi_table[SPAPR_PCI_NUM_LSI];
+    } lsi_table[PCI_NUM_PINS];
 
     QLIST_ENTRY(sPAPRPHBState) list;
 } sPAPRPHBState;