def get_disk_bus_for_device_type(virt_type,
image_meta,
device_type="disk",
instance=None):
"""Determine the best disk bus to use for a device type.
Considering the currently configured virtualization
type, return the optimal disk_bus to use for a given
device type. For example, for a disk on KVM it will
return 'virtio', while for a CDROM it will return 'ide'
on x86_64 and 'scsi' on ppc64.
Returns the disk_bus, or returns None if the device
type is not supported for this virtualization
"""
# Prefer a disk bus set against the image first of all
key = "hw_" + device_type + "_bus"
disk_bus = image_meta.get('properties', {}).get(key)
if disk_bus is not None:
if not is_disk_bus_valid_for_virt(virt_type, disk_bus):
raise exception.UnsupportedHardware(model=disk_bus, virt=virt_type)
return disk_bus
# Otherwise pick a hypervisor default disk bus
if virt_type == "uml":
if device_type == "disk":
return "uml"
elif virt_type == "lxc":
return "lxc"
elif virt_type == "xen":
guest_vm_mode = None
if instance:
guest_vm_mode = vm_mode.get_from_instance(instance)
if guest_vm_mode == vm_mode.HVM:
return "ide"
else:
return "xen"
elif virt_type in ("qemu", "kvm"):
if device_type == "cdrom":
guestarch = libvirt_utils.get_arch(image_meta)
if guestarch in (arch.PPC, arch.PPC64, arch.S390, arch.S390X):
return "scsi"
else:
return "ide"
elif device_type == "disk":
return "virtio"
elif device_type == "floppy":
return "fdc"
elif virt_type == "parallels":
if device_type == "cdrom":
return "ide"
elif device_type == "disk":
return "sata"
else:
# If virt-type not in list then it is unsupported
raise exception.UnsupportedVirtType(virt=virt_type)
return None
def test_good(self):
inst = self._fake_object(dict(vm_mode="hvm"))
mode = vm_mode.get_from_instance(inst)
self.assertEqual(mode, "hvm")
def test_legacy_pv(self):
inst = self._fake_object(dict(vm_mode="pv"))
mode = vm_mode.get_from_instance(inst)
self.assertEqual(mode, "xen")