[libvirt] [PATCH v2 1/2] qemu: fix type of default video device

[Pavel Mores]

If a graphics device is added to XML that has no video device, libvirt
automatically added a video device which was always of type 'cirrus' on
x86_64, even if the underlying qemu didn't support cirrus.

This patch refines a bit the decision about the type of the video device.
Based on QEMU capabilities, cirrus is still preferred but only added if
QEMU supports it, otherwise VGA is used if supported by QEMU.  There is now
no fallback as libvirt only aspires to generate a basic working config and
leaves anything more specific up to higher-level management tools.

https://bugzilla.redhat.com/show_bug.cgi?id=1668141
Signed-off-by: Pavel Mores <pmores at redhat.com>
---
 src/qemu/qemu_domain.c | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index b257db44b0..39b2d2da82 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -7360,6 +7360,28 @@ qemuDomainDefaultNetModel(const virDomainDef *def,
 }
 
 
+static int
+qemuDomainDefaultVideoDevice(const virDomainDef *def,
+                          virQEMUCapsPtr qemuCaps)
+{
+    if (ARCH_IS_PPC64(def->os.arch)) {
+        return VIR_DOMAIN_VIDEO_TYPE_VGA;
+    } else if (qemuDomainIsARMVirt(def) ||
+             qemuDomainIsRISCVVirt(def) ||
+             ARCH_IS_S390(def->os.arch)) {
+        return VIR_DOMAIN_VIDEO_TYPE_VIRTIO;
+    } else {
+        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_CIRRUS_VGA)) {
+            return VIR_DOMAIN_VIDEO_TYPE_CIRRUS;
+        } else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VGA)) {
+            return VIR_DOMAIN_VIDEO_TYPE_VGA;
+        } else {
+            return VIR_DOMAIN_VIDEO_TYPE_DEFAULT;
+        }
+    }
+}
+
+
 /*
  * Clear auto generated unix socket paths:
  *
@@ -7821,18 +7843,11 @@ qemuDomainDeviceNetDefPostParse(virDomainNetDefPtr net,
 
 static int
 qemuDomainDeviceVideoDefPostParse(virDomainVideoDefPtr video,
-                                  const virDomainDef *def)
+                                  const virDomainDef *def,
+                                  virQEMUCapsPtr qemuCaps)
 {
-    if (video->type == VIR_DOMAIN_VIDEO_TYPE_DEFAULT) {
-        if (ARCH_IS_PPC64(def->os.arch))
-            video->type = VIR_DOMAIN_VIDEO_TYPE_VGA;
-        else if (qemuDomainIsARMVirt(def) ||
-                 qemuDomainIsRISCVVirt(def) ||
-                 ARCH_IS_S390(def->os.arch))
-            video->type = VIR_DOMAIN_VIDEO_TYPE_VIRTIO;
-        else
-            video->type = VIR_DOMAIN_VIDEO_TYPE_CIRRUS;
-    }
+    if (video->type == VIR_DOMAIN_VIDEO_TYPE_DEFAULT)
+        video->type = qemuDomainDefaultVideoDevice(def, qemuCaps);
 
     if (video->type == VIR_DOMAIN_VIDEO_TYPE_QXL &&
         !video->vgamem) {
@@ -7926,7 +7941,7 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
         break;
 
     case VIR_DOMAIN_DEVICE_VIDEO:
-        ret = qemuDomainDeviceVideoDefPostParse(dev->data.video, def);
+        ret = qemuDomainDeviceVideoDefPostParse(dev->data.video, def, qemuCaps);
         break;
 
     case VIR_DOMAIN_DEVICE_PANIC:
-- 
2.21.0