hw/i386/pc_piix: Make piix_intx_routing_notifier_xen() more device independent

This is a follow-up on commit 89965db43cce "hw/isa/piix3: Avoid Xen-specific
variant of piix3_write_config()" which introduced
piix_intx_routing_notifier_xen(). This function is implemented in board code but
accesses the PCI configuration space of the PIIX ISA function to determine the
PCI interrupt routes. Avoid this by reusing pci_device_route_intx_to_irq() which
makes piix_intx_routing_notifier_xen() more device-agnostic.

One remaining improvement would be making piix_intx_routing_notifier_xen()
agnostic towards the number of PCI interrupt routes and move it to xen-hvm.
This might be useful for possible Q35 Xen efforts but remains a future exercise
for now.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240107231623.5282-1-shentey@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

1 files changed, 3 insertions, 6 deletions

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 042c13cdbc..abfcfe4d2b 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -92,13 +92,10 @@ static void piix_intx_routing_notifier_xen(PCIDevice *dev)
 {
     int i;
 
-    /* Scan for updates to PCI link routes (0x60-0x63). */
+    /* Scan for updates to PCI link routes. */
     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;
+        const PCIINTxRoute route = pci_device_route_intx_to_irq(dev, i);
+        const uint8_t v = route.mode == PCI_INTX_ENABLED ? route.irq : 0;
         xen_set_pci_link_route(i, v);
     }
 }