From 2b0024c04070dcffc056e9df7b9ced40cbfdcc00 Mon Sep 17 00:00:00 2001
From: Boris Bobrov <bbobrov@suse.com>
Date: Wed, 25 Sep 2019 20:07:50 +0200
Subject: [PATCH] Switch to uses_virtio to enable iommu driver for AMD SEV

In order to use AMD SEV, devices that use virtio should also use
iommu driver. The problem is to understand that a device uses virtio,
because there are many attributes and values that can indicate it.
For example, it can be `model='virtio'` for rng and
`<target bus='virtio'/>` for disk.

Add new property for devices `uses_virtio`, that will indicate that a
device in its current configuration is a virtio device, and implement it
for known devices.

The patch does not change how resulting libvirt XMLs look and does not
fix user-visible bugs. This refactoring is required for further work on
AMD SEV related patches.

The changes to memballoon-related tests were required because the tests
were using fake values that does are not possible in real life and that
were preventing tests of the new method. The tests now use the value
that nova currently uses to generate libvirt xml.

Change-Id: I0f85918996128d573b5dbd6ac49a9c2356cd40a9
Partial-Bug: #1845986
---
 nova/tests/unit/virt/libvirt/test_config.py | 21 +++++++++++++++------
 nova/virt/libvirt/config.py                 | 20 ++++++++++++++++++++
 nova/virt/libvirt/designer.py               | 11 +----------
 3 files changed, 36 insertions(+), 16 deletions(-)

diff --git a/nova/tests/unit/virt/libvirt/test_config.py b/nova/tests/unit/virt/libvirt/test_config.py
index 1cc39c29b7b4..2fa19e0a38e3 100644
--- a/nova/tests/unit/virt/libvirt/test_config.py
+++ b/nova/tests/unit/virt/libvirt/test_config.py
@@ -1836,6 +1836,7 @@ class LibvirtConfigGuestInterfaceTest(LibvirtConfigBaseTest):
         obj.mac_addr = "DE:AD:BE:EF:CA:FE"
         obj.model = "virtio"
         obj.target_dev = "vnet0"
+        self.assertTrue(obj.uses_virtio)
         return obj
 
     def test_config_driver_options(self):
@@ -2859,6 +2860,8 @@ class LibvirtConfigGuestSnapshotTest(LibvirtConfigBaseTest):
         obj.target_bus = "virtio"
         obj.serial = "7a97c4a3-6f59-41d4-bf47-191d7f97f8e9"
 
+        self.assertTrue(obj.uses_virtio)
+
         xml = obj.to_xml()
         self.assertXmlEqual("""
             <disk type="file" device="disk">
@@ -3265,6 +3268,8 @@ class LibvirtConfigGuestVideoTest(LibvirtConfigBaseTest):
         obj = config.LibvirtConfigGuestVideo()
         obj.type = 'qxl'
 
+        self.assertFalse(obj.uses_virtio)
+
         xml = obj.to_xml()
         self.assertXmlEqual(xml, """
                 <video>
@@ -3333,6 +3338,8 @@ class LibvirtConfigGuestRngTest(LibvirtConfigBaseTest):
         obj = config.LibvirtConfigGuestRng()
         obj.driver_iommu = True
 
+        self.assertTrue(obj.uses_virtio)
+
         xml = obj.to_xml()
         self.assertXmlEqual(xml, """
             <rng model='virtio'>
@@ -3667,12 +3674,12 @@ class LibvirtConfigMemoryBalloonTest(LibvirtConfigBaseTest):
 
     def test_config_memory_balloon_period(self):
         balloon = config.LibvirtConfigMemoryBalloon()
-        balloon.model = 'fake_virtio'
+        balloon.model = 'virtio'
         balloon.period = 11
 
         xml = balloon.to_xml()
         expected_xml = """
-        <memballoon model='fake_virtio'>
+        <memballoon model='virtio'>
             <stats period='11'/>
         </memballoon>"""
 
@@ -3680,22 +3687,24 @@ class LibvirtConfigMemoryBalloonTest(LibvirtConfigBaseTest):
 
     def test_config_memory_balloon_no_period(self):
         balloon = config.LibvirtConfigMemoryBalloon()
-        balloon.model = 'fake_virtio'
+        balloon.model = 'virtio'
 
         xml = balloon.to_xml()
         expected_xml = """
-        <memballoon model='fake_virtio' />"""
+        <memballoon model='virtio' />"""
 
         self.assertXmlEqual(expected_xml, xml)
 
     def test_config_memory_balloon_driver_iommu(self):
         balloon = config.LibvirtConfigMemoryBalloon()
-        balloon.model = 'fake_virtio'
+        balloon.model = 'virtio'
         balloon.driver_iommu = True
 
+        self.assertTrue(balloon.uses_virtio)
+
         xml = balloon.to_xml()
         expected_xml = """
-            <memballoon model='fake_virtio'>
+            <memballoon model='virtio'>
               <driver iommu="on" />
             </memballoon>"""
 
diff --git a/nova/virt/libvirt/config.py b/nova/virt/libvirt/config.py
index b67b112cc8ec..99ed468ddaee 100644
--- a/nova/virt/libvirt/config.py
+++ b/nova/virt/libvirt/config.py
@@ -875,6 +875,10 @@ class LibvirtConfigGuestDevice(LibvirtConfigObject):
     def __init__(self, **kwargs):
         super(LibvirtConfigGuestDevice, self).__init__(**kwargs)
 
+    @property
+    def uses_virtio(self):
+        return False
+
 
 class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
 
@@ -984,6 +988,10 @@ class LibvirtConfigGuestDisk(LibvirtConfigGuestDevice):
         if len(iotune) > 0:
             dev.append(iotune)
 
+    @property
+    def uses_virtio(self):
+        return 'virtio' == self.target_bus
+
     def format_dom(self):
         dev = super(LibvirtConfigGuestDisk, self).format_dom()
 
@@ -1573,6 +1581,10 @@ class LibvirtConfigGuestInterface(LibvirtConfigGuestDevice):
         self.device_addr = None
         self.mtu = None
 
+    @property
+    def uses_virtio(self):
+        return 'virtio' == self.model
+
     def format_dom(self):
         dev = super(LibvirtConfigGuestInterface, self).format_dom()
 
@@ -1890,6 +1902,10 @@ class LibvirtConfigMemoryBalloon(LibvirtConfigGuestDevice):
         self.period = None
         self.driver_iommu = False
 
+    @property
+    def uses_virtio(self):
+        return 'virtio' == self.model
+
     def format_dom(self):
         dev = super(LibvirtConfigMemoryBalloon, self).format_dom()
         dev.set('model', str(self.model))
@@ -3016,6 +3032,10 @@ class LibvirtConfigGuestRng(LibvirtConfigGuestDevice):
         self.rate_bytes = None
         self.driver_iommu = False
 
+    @property
+    def uses_virtio(self):
+        return 'virtio' == self.device_model
+
     def format_dom(self):
         dev = super(LibvirtConfigGuestRng, self).format_dom()
         dev.set('model', self.device_model)
diff --git a/nova/virt/libvirt/designer.py b/nova/virt/libvirt/designer.py
index 793f1f17cdb1..7bafd47bbcbd 100644
--- a/nova/virt/libvirt/designer.py
+++ b/nova/virt/libvirt/designer.py
@@ -21,7 +21,6 @@ classes based on common operational needs / policies
 
 
 from nova.pci import utils as pci_utils
-from nova.virt.libvirt import config
 
 MIN_LIBVIRT_ETHERNET_SCRIPT_PATH_NONE = (1, 3, 3)
 
@@ -200,14 +199,6 @@ def set_vcpu_realtime_scheduler(conf, vcpus_rt, priority):
 
 
 def set_driver_iommu_for_sev(conf):
-    virtio_attrs = {
-        config.LibvirtConfigGuestDisk: 'target_bus',
-        config.LibvirtConfigGuestInterface: 'model',
-        config.LibvirtConfigGuestRng: 'device_model',
-        config.LibvirtConfigMemoryBalloon: 'model',
-    }
-
     for dev in conf.devices:
-        virtio_attr = virtio_attrs.get(dev.__class__)
-        if virtio_attr and getattr(dev, virtio_attr) == 'virtio':
+        if dev.uses_virtio:
             dev.driver_iommu = True