KVM: actually support different nic types

When executing the KVM runtime we load the nic type from the runtime
hvparams and use it to specify the nic model type. As for the disk we
translate the DEV_PARAVIRTUAL type to 'virtio'.

Reviewed-by: iustinp

lib/hypervisor/hv_kvm.py

@@ -393,8 +393,14 @@ class KVMHypervisor(hv_base.BaseHypervisor):
     if not kvm_nics:
       kvm_cmd.extend(['-net', 'none'])
     else:
+      nic_type = hvparams[constants.HV_NIC_TYPE]
+      if nic_type == constants.HT_NIC_PARAVIRTUAL:
+        nic_model = "model=virtio"
+      else:
+        nic_model = "model=%s" % nic_type
+
       for nic_seq, nic in enumerate(kvm_nics):
-        nic_val = "nic,macaddr=%s,model=virtio" % nic.mac
+        nic_val = "nic,macaddr=%s,%s" % (nic.mac, nic_model)
         script = self._WriteNetScript(instance, nic_seq, nic)
         kvm_cmd.extend(['-net', nic_val])
         kvm_cmd.extend(['-net', 'tap,script=%s' % script])