diff --git a/hw/ide/pci.c b/hw/ide/pci.c
index a25b352537..810c6b6d98 100644
--- a/hw/ide/pci.c
+++ b/hw/ide/pci.c
@@ -104,6 +104,90 @@ const MemoryRegionOps pci_ide_data_le_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
+void pci_ide_update_mode(PCIIDEState *s)
+{
+    PCIDevice *d = PCI_DEVICE(s);
+    uint8_t mode = d->config[PCI_CLASS_PROG];
+
+    /*
+     * This function only configures the BARs/ioports for now: PCI IDE
+     * controllers must manage their own IRQ routing
+     */
+
+    switch (mode & 0xf) {
+    case 0xa:
+        /* Both channels legacy mode */
+
+        /*
+         * TODO: according to the PCI IDE specification the BARs should
+         * be completely disabled, however Linux for the pegasos2
+         * machine stil accesses the BAR addresses after switching to legacy
+         * mode. Hence we leave them active for now.
+         */
+
+        /* Clear interrupt pin */
+        pci_config_set_interrupt_pin(d->config, 0);
+
+        /* Add legacy IDE ports */
+        if (!s->bus[0].portio_list.owner) {
+            portio_list_init(&s->bus[0].portio_list, OBJECT(d),
+                             ide_portio_list, &s->bus[0], "ide");
+            portio_list_add(&s->bus[0].portio_list,
+                            pci_address_space_io(d), 0x1f0);
+        }
+
+        if (!s->bus[0].portio2_list.owner) {
+            portio_list_init(&s->bus[0].portio2_list, OBJECT(d),
+                             ide_portio2_list, &s->bus[0], "ide");
+            portio_list_add(&s->bus[0].portio2_list,
+                            pci_address_space_io(d), 0x3f6);
+        }
+
+        if (!s->bus[1].portio_list.owner) {
+            portio_list_init(&s->bus[1].portio_list, OBJECT(d),
+                                ide_portio_list, &s->bus[1], "ide");
+            portio_list_add(&s->bus[1].portio_list,
+                            pci_address_space_io(d), 0x170);
+        }
+
+        if (!s->bus[1].portio2_list.owner) {
+            portio_list_init(&s->bus[1].portio2_list, OBJECT(d),
+                             ide_portio2_list, &s->bus[1], "ide");
+            portio_list_add(&s->bus[1].portio2_list,
+                            pci_address_space_io(d), 0x376);
+        }
+        break;
+
+    case 0xf:
+        /* Both channels native mode */
+
+        /* Set interrupt pin */
+        pci_config_set_interrupt_pin(d->config, 1);
+
+        /* Remove legacy IDE ports */
+        if (s->bus[0].portio_list.owner) {
+            portio_list_del(&s->bus[0].portio_list);
+            portio_list_destroy(&s->bus[0].portio_list);
+        }
+
+        if (s->bus[0].portio2_list.owner) {
+            portio_list_del(&s->bus[0].portio2_list);
+            portio_list_destroy(&s->bus[0].portio2_list);
+        }
+
+        if (s->bus[1].portio_list.owner) {
+            portio_list_del(&s->bus[1].portio_list);
+            portio_list_destroy(&s->bus[1].portio_list);
+        }
+
+        if (s->bus[1].portio2_list.owner) {
+            portio_list_del(&s->bus[1].portio2_list);
+            portio_list_destroy(&s->bus[1].portio2_list);
+        }
+        break;
+    }
+}
+
 static IDEState *bmdma_active_if(BMDMAState *bmdma)
 {
     assert(bmdma->bus->retry_unit != (uint8_t)-1);
diff --git a/include/hw/ide/pci.h b/include/hw/ide/pci.h
index 1ff469de87..a814a0a7c3 100644
--- a/include/hw/ide/pci.h
+++ b/include/hw/ide/pci.h
@@ -61,6 +61,7 @@ void bmdma_cmd_writeb(BMDMAState *bm, uint32_t val);
 void bmdma_status_writeb(BMDMAState *bm, uint32_t val);
 extern MemoryRegionOps bmdma_addr_ioport_ops;
 void pci_ide_create_devs(PCIDevice *dev);
+void pci_ide_update_mode(PCIIDEState *s);
 
 extern const VMStateDescription vmstate_ide_pci;
 extern const MemoryRegionOps pci_ide_cmd_le_ops;