[libvirt] [PATCH v2 2/2] qemu: Default to virtio-net where available

[Andrea Bolognani]

This applies to all architectures except for ARM, which already
has its own logic to pick the best default.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1254044
---
Changes from v1:

  * make sure virtio-net is available using capabilities
    instead of blindly using it (thanks Martin)

  * change the default for all architectures (except arm)
    instead of just ppc64

 src/qemu/qemu_domain.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 0a9ed6b..8f4efd3 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -1193,11 +1193,9 @@ qemuDomainDefPostParse(virDomainDefPtr def,
 }
 
 static const char *
-qemuDomainDefaultNetModel(const virDomainDef *def)
+qemuDomainDefaultNetModel(const virDomainDef *def,
+                          virQEMUCapsPtr qemuCaps)
 {
-    if (ARCH_IS_S390(def->os.arch))
-        return "virtio";
-
     if (def->os.arch == VIR_ARCH_ARMV7L ||
         def->os.arch == VIR_ARCH_AARCH64) {
         if (STREQ(def->os.machine, "versatilepb"))
@@ -1211,6 +1209,10 @@ qemuDomainDefaultNetModel(const virDomainDef *def)
         return "lan9118";
     }
 
+    /* virtio should always be used where available */
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VIRTIO_NET))
+        return "virtio";
+
     return "rtl8139";
 }
 
@@ -1223,15 +1225,21 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
     int ret = -1;
     virQEMUDriverPtr driver = opaque;
     virQEMUDriverConfigPtr cfg = NULL;
+    virQEMUCapsPtr qemuCaps = NULL;
 
     if (driver)
         cfg = virQEMUDriverGetConfig(driver);
 
+    /* This condition is actually a (temporary) hack for test suite which
+     * does not create capabilities cache */
+    if (driver && driver->qemuCapsCache)
+        qemuCaps = virQEMUCapsCacheLookup(driver->qemuCapsCache, def->emulator);
+
     if (dev->type == VIR_DOMAIN_DEVICE_NET &&
         dev->data.net->type != VIR_DOMAIN_NET_TYPE_HOSTDEV &&
         !dev->data.net->model) {
         if (VIR_STRDUP(dev->data.net->model,
-                       qemuDomainDefaultNetModel(def)) < 0)
+                       qemuDomainDefaultNetModel(def, qemuCaps)) < 0)
             goto cleanup;
     }
 
@@ -1358,6 +1366,7 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
 
  cleanup:
     virObjectUnref(cfg);
+    virObjectUnref(qemuCaps);
     return ret;
 }
 
-- 
2.4.3