Change default PCI class of virtio-console to PCI_CLASS_SERIAL_OTHER

We're using PCI_CLASS_DISPLAY_OTHER now, but qemu-kvm.git is using
PCI_CLASS_OTHERS because:

  "As a PCI_CLASS_DISPLAY_OTHER, it reduces primary display somehow on
   Windows XP (possibly Windows disables acceleration since it fails
   to find a driver)."

While this is valid, many versions of X will get confused by it.
Class major number of 0 gets treated as a possibly prehistoric VGA
device, and then the autoconfig logic gets confused trying to figure
out whether the virtio console or the pv vga device are the real VGA.

We should really set a proper class ID. 0x0780 (serial / other) seems
most appropriate. This shouldn't require any kernel changes, the
modalias for virtio looks like:

  alias:          pci:v00001AF4d*sv*sd*bc*sc*i*

so won't care what the base class or subclass are.

It shows up in the guest as:

  00:05.0 Communication controller: Qumranet, Inc. Virtio console

A new qdev type is introduced to allow devices using the old class
to be created for compatibility with qemu-0.10.x.
Reported-by: NAdam Jackson <ajax@redhat.com>
Signed-off-by: NMark McLoughlin <markmc@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pci_ids.h

@@ -35,6 +35,9 @@
 #define PCI_CLASS_BRIDGE_PCI             0x0604
 #define PCI_CLASS_BRIDGE_OTHER           0x0680
 
+#define PCI_CLASS_SERIAL_OTHER           0x0780
+
+#define PCI_CLASS_PROCESSOR_CO           0x0b40
 #define PCI_CLASS_COMMUNICATION_OTHER    0x0780
 
 #define PCI_CLASS_PROCESSOR_CO           0x0b40

hw/virtio-pci.c

@@ -449,7 +449,8 @@ static void virtio_blk_init_pci_0_10(PCIDevice *pci_dev)
     virtio_blk_init_pci_with_class(pci_dev, PCI_CLASS_STORAGE_OTHER);
 }
 
-static void virtio_console_init_pci(PCIDevice *pci_dev)
+static void virtio_console_init_pci_with_class(PCIDevice *pci_dev,
+                                               uint16_t class_code)
 {
     VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
     VirtIODevice *vdev;
@@ -458,8 +459,17 @@ static void virtio_console_init_pci(PCIDevice *pci_dev)
     virtio_init_pci(proxy, vdev,
                     PCI_VENDOR_ID_REDHAT_QUMRANET,
                     PCI_DEVICE_ID_VIRTIO_CONSOLE,
-                    PCI_CLASS_DISPLAY_OTHER,
-                    0x00);
+                    class_code, 0x00);
+}
+
+static void virtio_console_init_pci(PCIDevice *pci_dev)
+{
+    virtio_console_init_pci_with_class(pci_dev, PCI_CLASS_SERIAL_OTHER);
+}
+
+static void virtio_console_init_pci_0_10(PCIDevice *pci_dev)
+{
+    virtio_console_init_pci_with_class(pci_dev, PCI_CLASS_DISPLAY_OTHER);
 }
 
 static void virtio_net_init_pci(PCIDevice *pci_dev)
@@ -510,6 +520,10 @@ static PCIDeviceInfo virtio_info[] = {
         .qdev.name = "virtio-blk-pci-0-10",
         .qdev.size = sizeof(VirtIOPCIProxy),
         .init      = virtio_blk_init_pci_0_10,
+    },{
+        .qdev.name = "virtio-console-pci-0-10",
+        .qdev.size = sizeof(VirtIOPCIProxy),
+        .init      = virtio_console_init_pci_0_10,
     },{
         /* end of list */
     }