diff --git a/tools/ioemu/hw/cirrus_vga.c b/tools/ioemu/hw/cirrus_vga.c
index 3c316d6dc9..292673ae6a 100644
--- a/tools/ioemu/hw/cirrus_vga.c
+++ b/tools/ioemu/hw/cirrus_vga.c
@@ -3339,6 +3339,10 @@ void pci_cirrus_vga_init(PCIBus *bus, DisplayState *ds, uint8_t *vga_ram_base,
     pci_conf[0x0a] = PCI_CLASS_SUB_VGA;
     pci_conf[0x0b] = PCI_CLASS_BASE_DISPLAY;
     pci_conf[0x0e] = PCI_CLASS_HEADERTYPE_00h;
+    pci_conf[0x2c] = 0x53; /* subsystem vendor: XenSource */
+    pci_conf[0x2d] = 0x58;
+    pci_conf[0x2e] = 0x01; /* subsystem device */
+    pci_conf[0x2f] = 0x00;
 
     /* setup VGA */
     s = &d->cirrus_vga;
diff --git a/tools/ioemu/hw/ide.c b/tools/ioemu/hw/ide.c
index ef203a2f8a..3bf2c7d594 100644
--- a/tools/ioemu/hw/ide.c
+++ b/tools/ioemu/hw/ide.c
@@ -2502,6 +2502,10 @@ void pci_piix3_ide_init(PCIBus *bus, BlockDriverState **hd_table, int devfn)
     pci_conf[0x0a] = 0x01; // class_sub = PCI_IDE
     pci_conf[0x0b] = 0x01; // class_base = PCI_mass_storage
     pci_conf[0x0e] = 0x00; // header_type
+    pci_conf[0x2c] = 0x53; /* subsystem vendor: XenSource */
+    pci_conf[0x2d] = 0x58;
+    pci_conf[0x2e] = 0x01; /* subsystem device */
+    pci_conf[0x2f] = 0x00;
 
     pci_register_io_region((PCIDevice *)d, 4, 0x10, 
                            PCI_ADDRESS_SPACE_IO, bmdma_map);
diff --git a/tools/ioemu/hw/rtl8139.c b/tools/ioemu/hw/rtl8139.c
index 77e3c6d9fb..e4ba40dfe3 100644
--- a/tools/ioemu/hw/rtl8139.c
+++ b/tools/ioemu/hw/rtl8139.c
@@ -3423,8 +3423,10 @@ void pci_rtl8139_init(PCIBus *bus, NICInfo *nd)
     pci_conf[0x0e] = 0x00; /* header_type */
     pci_conf[0x3d] = 1;    /* interrupt pin 0 */
     pci_conf[0x34] = 0xdc;
-    pci_conf[0x2c] = pci_conf[0x00]; // same as Vendor ID
-    pci_conf[0x2d] = pci_conf[0x01];
+    pci_conf[0x2c] = 0x53; /* subsystem vendor: XenSource */
+    pci_conf[0x2d] = 0x58;
+    pci_conf[0x2e] = 0x01; /* subsystem device */
+    pci_conf[0x2f] = 0x00;
 
     s = &d->rtl8139;