qemu: error out on missing machine type in configs

Commit f1a89a8b allowed parsing configs from /etc/libvirt
without validating the emulator capabilities.

Check for the presence of a machine type in the qemu driver's
post parse function instead of crashing.

https://bugzilla.redhat.com/show_bug.cgi?id=1267256

src/qemu/qemu_domain.c

@@ -1307,6 +1307,12 @@ qemuDomainDefPostParse(virDomainDefPtr def,
         return ret;
     }
 
+    if (!def->os.machine) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("missing machine type"));
+        return ret;
+    }
+
     /* check for emulator and create a default one if needed */
     if (!def->emulator &&
         !(def->emulator = virDomainDefGetDefaultEmulator(def, caps)))

tests/qemuxml2argvdata/qemuxml2argv-missing-machine.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <title>A description of the test machine.</title>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static' cpuset='1'>1</vcpu>
+  <os>
+    <type arch='i686'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -571,6 +571,10 @@ mymain(void)
                  FLAG_EXPECT_PARSE_ERROR | FLAG_EXPECT_ERROR,           \
                  0, __VA_ARGS__)
 
+# define DO_TEST_PARSE_FLAGS_ERROR(name, parseFlags, ...)               \
+    DO_TEST_FULL(name, NULL, -1,                                        \
+                 FLAG_EXPECT_PARSE_ERROR | FLAG_EXPECT_ERROR,           \
+                 parseFlags, __VA_ARGS__)
 
 # define DO_TEST_LINUX(name, ...)                                       \
     DO_TEST_LINUX_FULL(name, NULL, -1, 0, 0, __VA_ARGS__)
@@ -1868,6 +1872,10 @@ mymain(void)
     DO_TEST("ppc64-usb-controller-legacy",
             QEMU_CAPS_PIIX3_USB_UHCI);
 
+    DO_TEST_PARSE_FLAGS_ERROR("missing-machine",
+                              VIR_DOMAIN_DEF_PARSE_SKIP_OSTYPE_CHECKS,
+                              NONE);
+
     qemuTestDriverFree(&driver);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;