qemu/pci: reset device registers on bus reset

Reset BARs and a couple of other registers on bus reset, as per PCI
spec.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pci.c

@@ -92,7 +92,20 @@ static inline int pci_bar(int reg)
 
 static void pci_device_reset(PCIDevice *dev)
 {
+    int r;
+
     memset(dev->irq_state, 0, sizeof dev->irq_state);
+    dev->config[PCI_COMMAND] &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
+                                  PCI_COMMAND_MASTER);
+    dev->config[PCI_CACHE_LINE_SIZE] = 0x0;
+    dev->config[PCI_INTERRUPT_LINE] = 0x0;
+    for (r = 0; r < PCI_NUM_REGIONS; ++r) {
+        if (!dev->io_regions[r].size) {
+            continue;
+        }
+        pci_set_long(dev->config + pci_bar(r), dev->io_regions[r].type);
+    }
+    pci_update_mappings(dev);
 }
 
 static void pci_bus_reset(void *opaque)