Since we hijacked the OpenBSD PCI vendor ID, this diff should probably
not be upstreamed.

Index: src/fw/pciinit.c
--- src/fw/pciinit.c.orig
+++ src/fw/pciinit.c
@@ -142,6 +142,11 @@ static int mch_pci_slot_get_irq(struct pci_device *pci
     return pci_irqs[(pin - 1 + pin_addend) & 3];
 }
 
+static int vmm_pci_slot_get_irq(struct pci_device *pci, int pin)
+{
+    return pci_config_readb(pci->bdf, PCI_INTERRUPT_LINE);
+}
+
 /* PIIX3/PIIX4 PCI to ISA bridge */
 static void piix_isa_bridge_setup(struct pci_device *pci, void *arg)
 {
@@ -505,11 +510,18 @@ static void mch_mem_addr_setup(struct pci_device *dev,
         pci_io_low_end = acpi_pm_base;
 }
 
+static void vmm_mem_addr_setup(struct pci_device *dev, void *arg)
+{
+    pci_slot_get_irq = vmm_pci_slot_get_irq;
+}
+
 static const struct pci_device_id pci_platform_tbl[] = {
     PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82441,
                i440fx_mem_addr_setup),
     PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_Q35_MCH,
                mch_mem_addr_setup),
+    PCI_DEVICE(PCI_VENDOR_ID_OPENBSD, PCI_DEVICE_ID_OPENBSD_PCHB,
+	       vmm_mem_addr_setup),
     PCI_DEVICE_END
 };