1 files changed, 33 insertions, 3 deletions

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index d5b0dcd1fe..42af03dbb4 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -71,6 +71,7 @@
 #include "kvm/kvm-cpu.h"
 
 #define MAX_IDE_BUS 2
+#define XEN_IOAPIC_NUM_PIRQS 128ULL
 
 #ifdef CONFIG_IDE_ISA
 static const int ide_iobase[MAX_IDE_BUS] = { 0x1f0, 0x170 };
@@ -89,6 +90,21 @@ static int pc_pci_slot_get_pirq(PCIDevice *pci_dev, int pci_intx)
     return (pci_intx + slot_addend) & 3;
 }
 
+static void piix_intx_routing_notifier_xen(PCIDevice *dev)
+{
+    int i;
+
+    /* Scan for updates to PCI link routes (0x60-0x63). */
+    for (i = 0; i < PIIX_NUM_PIRQS; i++) {
+        uint8_t v = dev->config_read(dev, PIIX_PIRQCA + i, 1);
+        if (v & 0x80) {
+            v = 0;
+        }
+        v &= 0xf;
+        xen_set_pci_link_route(i, v);
+    }
+}
+
 /* PC hardware initialisation */
 static void pc_init1(MachineState *machine,
                      const char *host_type, const char *pci_type)
@@ -223,8 +239,6 @@ static void pc_init1(MachineState *machine,
     if (pcmc->pci_enabled) {
         PIIX3State *piix3;
         PCIDevice *pci_dev;
-        const char *type = xen_enabled() ? TYPE_PIIX3_XEN_DEVICE
-                                         : TYPE_PIIX3_DEVICE;
 
         pci_bus = i440fx_init(pci_type,
                               i440fx_host,
@@ -237,7 +251,23 @@ static void pc_init1(MachineState *machine,
                                        : pc_pci_slot_get_pirq);
         pcms->bus = pci_bus;
 
-        pci_dev = pci_create_simple_multifunction(pci_bus, -1, true, type);
+        pci_dev = pci_create_simple_multifunction(pci_bus, -1, true,
+                                                  TYPE_PIIX3_DEVICE);
+
+        if (xen_enabled()) {
+            pci_device_set_intx_routing_notifier(
+                        pci_dev, piix_intx_routing_notifier_xen);
+
+            /*
+             * Xen supports additional interrupt routes from the PCI devices to
+             * the IOAPIC: the four pins of each PCI device on the bus are also
+             * connected to the IOAPIC directly.
+             * These additional routes can be discovered through ACPI.
+             */
+            pci_bus_irqs(pci_bus, xen_intx_set_irq, pci_dev,
+                         XEN_IOAPIC_NUM_PIRQS);
+        }
+
         piix3 = PIIX3_PCI_DEVICE(pci_dev);
         piix3->pic = x86ms->gsi;
         piix3_devfn = piix3->dev.devfn;