From 66a7f044f5143feaf7046cebafea3df3ea95e04b Mon Sep 17 00:00:00 2001
From: "Daniel P. Berrange" <berrange@redhat.com>
Date: Wed, 16 Jan 2013 12:38:23 +0000
Subject: Allow disk driver to be chosen per image

This allows for an image in glance to be annotated with a
property describing the required disk / cdrom bus type.

eg

  # glance image-update \
           --property disk_bus=ide \
           --property cdrom_bus=ide \
           f16-x86_64-openstack-sda

Valid bus values vary per the libvirt_type setting:

 qemu/kvm: 'virtio', 'scsi', 'ide', 'usb'
 xen: 'xen', 'ide'
 uml: 'uml'

Requesting an unsupported disk bus will cause the guest
instance to fail to launch.

DocImpact
Blueprint: libvirt-custom-hardware
Change-Id: Ibc20b843ceccf374eae246384a3f246cc1c52a28
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 nova/tests/test_libvirt_blockinfo.py | 31 +++++++++++++++++++++++++++++++
 nova/virt/libvirt/blockinfo.py       | 35 ++++++++++++++++++++++++++++++++---
 2 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/nova/tests/test_libvirt_blockinfo.py b/nova/tests/test_libvirt_blockinfo.py
index 23f846324..e8d548399 100644
--- a/nova/tests/test_libvirt_blockinfo.py
+++ b/nova/tests/test_libvirt_blockinfo.py
@@ -18,6 +18,7 @@
 from nova import block_device
 from nova import context
 from nova import db
+from nova import exception
 from nova import test
 import nova.tests.image.fake
 from nova.virt.libvirt import blockinfo
@@ -394,3 +395,33 @@ class LibvirtBlockInfoTest(test.TestCase):
             'root': {'bus': 'virtio', 'dev': 'vdf', 'type': 'disk'}
             }
         self.assertEqual(mapping, expect)
+
+    def test_get_disk_bus(self):
+        bus = blockinfo.get_disk_bus_for_device_type('kvm')
+        self.assertEqual(bus, 'virtio')
+
+        bus = blockinfo.get_disk_bus_for_device_type('kvm',
+                                                     device_type='cdrom')
+        self.assertEqual(bus, 'ide')
+
+        image_meta = {'properties': {'disk_bus': 'scsi'}}
+        bus = blockinfo.get_disk_bus_for_device_type('kvm',
+                                                     image_meta)
+        self.assertEqual(bus, 'scsi')
+
+        image_meta = {'properties': {'disk_bus': 'usb',
+                                     'cdrom_bus': 'scsi'}}
+        bus = blockinfo.get_disk_bus_for_device_type('kvm',
+                                                     image_meta,
+                                                     device_type='cdrom')
+        self.assertEqual(bus, 'scsi')
+
+        bus = blockinfo.get_disk_bus_for_device_type('kvm',
+                                                     image_meta)
+        self.assertEqual(bus, 'usb')
+
+        image_meta = {'properties': {'disk_bus': 'xen'}}
+        self.assertRaises(exception.NovaException,
+                          blockinfo.get_disk_bus_for_device_type,
+                          'kvm',
+                          image_meta)
diff --git a/nova/virt/libvirt/blockinfo.py b/nova/virt/libvirt/blockinfo.py
index 844ae4a1b..fc4a7dbfb 100644
--- a/nova/virt/libvirt/blockinfo.py
+++ b/nova/virt/libvirt/blockinfo.py
@@ -166,7 +166,24 @@ def find_disk_dev_for_disk_bus(mapping, bus, last_device=False):
         dev_prefix)
 
 
-def get_disk_bus_for_device_type(virt_type, device_type="disk"):
+def is_disk_bus_valid_for_virt(virt_type, disk_bus):
+        valid_bus = {
+            'qemu': ['virtio', 'scsi', 'ide', 'usb'],
+            'kvm': ['virtio', 'scsi', 'ide', 'usb'],
+            'xen': ['xen', 'ide'],
+            'uml': ['uml'],
+            }
+
+        if virt_type not in valid_bus:
+            raise exception.NovaException(
+                _("Unsupported virt type %s") % virt_type)
+
+        return disk_bus in valid_bus[virt_type]
+
+
+def get_disk_bus_for_device_type(virt_type,
+                                 image_meta=None,
+                                 device_type="disk"):
     """Determine the best disk bus to use for a device type.
 
        Considering the currently configured virtualization
@@ -177,6 +194,18 @@ def get_disk_bus_for_device_type(virt_type, device_type="disk"):
        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
+    if image_meta:
+        key = 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.NovaException(
+                    _("Disk bus %(disk_bus)s is not valid for %(virt)s") %
+                    {'disk_bus': 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"
@@ -375,8 +404,8 @@ def get_disk_info(virt_type, instance, block_device_info=None,
 
        Returns the disk mapping disk."""
 
-    disk_bus = get_disk_bus_for_device_type(virt_type, "disk")
-    cdrom_bus = get_disk_bus_for_device_type(virt_type, "cdrom")
+    disk_bus = get_disk_bus_for_device_type(virt_type, image_meta, "disk")
+    cdrom_bus = get_disk_bus_for_device_type(virt_type, image_meta, "cdrom")
     mapping = get_disk_mapping(virt_type, instance,
                                disk_bus, cdrom_bus,
                                block_device_info,
-- 
cgit