usb-msd: Propagate removable bit to SCSI device

USB Mass Storage Devices sometimes have the RMB (removable) bit set in
the SCSI INQUIRY response.  Thumbdrives tend to have the bit set whereas
hard disks do not.

Operating systems differentiate between removable devices and fixed
devices.  Under Linux, the anaconda installer looks for removable
devices.  Under Windows, only fixed devices may have more than one
partition and AutoRun is also affected by the removable bit.

For these reasons, allow USB Mass Storage Devices to override the
removable bit:

qemu -usb
     -drive if=none,file=test.img,cache=none,id=disk0
     -device usb-storage,drive=disk0,removable=on

The default is off.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/usb-msd.c

@@ -51,6 +51,7 @@ typedef struct {
     SCSIBus bus;
     BlockConf conf;
     SCSIDevice *scsi_dev;
+    uint32_t removable;
     int result;
     /* For async completion.  */
     USBPacket *packet;
@@ -515,7 +516,7 @@ static int usb_msd_initfn(USBDevice *dev)
 
     usb_desc_init(dev);
     scsi_bus_new(&s->bus, &s->dev.qdev, 0, 1, usb_msd_command_complete);
-    s->scsi_dev = scsi_bus_legacy_add_drive(&s->bus, bs, 0, false);
+    s->scsi_dev = scsi_bus_legacy_add_drive(&s->bus, bs, 0, !!s->removable);
     if (!s->scsi_dev) {
         return -1;
     }
@@ -607,6 +608,7 @@ static struct USBDeviceInfo msd_info = {
     .usbdevice_init = usb_msd_init,
     .qdev.props     = (Property[]) {
         DEFINE_BLOCK_PROPERTIES(MSDState, conf),
+        DEFINE_PROP_BIT("removable", MSDState, removable, 0, false),
         DEFINE_PROP_END_OF_LIST(),
     },
 };