pci: Add pci_device_route_intx_to_irq

Device assigned on KVM needs to know the mode
(enabled/inverted/disabled) and the IRQ number that a given device
triggers in the attached interrupt controller.

Add a PCI IRQ path discovery function that walks from a given device to
the host bridge, and gets this information.  For
this purpose, a host bridge callback function is introduced:
route_intx_to_irq. It is so far only implemented by the PIIX3, other
host bridges can be added later on as required.

Will be used for KVM PCI device assignment and VFIO.

Based on patch by Jan Kiszka, with minor tweaks.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/hw/pci.c b/hw/pci.c
index ef7607e177..e80599f058 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1066,6 +1066,26 @@ static void pci_set_irq(void *opaque, int irq_num, int level)
     pci_change_irq_level(pci_dev, irq_num, change);
 }
 
+/* Special hooks used by device assignment */
+void pci_bus_set_route_irq_fn(PCIBus *bus, pci_route_irq_fn route_intx_to_irq)
+{
+    assert(!bus->parent_dev);
+    bus->route_intx_to_irq = route_intx_to_irq;
+}
+
+PCIINTxRoute pci_device_route_intx_to_irq(PCIDevice *dev, int pin)
+{
+    PCIBus *bus;
+
+    do {
+         bus = dev->bus;
+         pin = bus->map_irq(dev, pin);
+         dev = bus->parent_dev;
+    } while (dev);
+    assert(bus->route_intx_to_irq);
+    return bus->route_intx_to_irq(bus->irq_opaque, pin);
+}
+
 /***********************************************************/
 /* monitor info on PCI */