qemu: Don't add default memballoon device on ARM

And add test cases for a basic working ARM guest.

docs/schemas/domaincommon.rng

@@ -304,6 +304,7 @@
           <ref name="hvmppc"/>
           <ref name="hvmppc64"/>
           <ref name="hvms390"/>
+          <ref name="hvmarm"/>
         </choice>
       </optional>
       <value>hvm</value>
@@ -413,6 +414,24 @@
       </optional>
     </group>
   </define>
+  <define name="hvmarm">
+    <group>
+      <optional>
+        <attribute name="arch">
+          <choice>
+            <value>armv7l</value>
+          </choice>
+        </attribute>
+      </optional>
+      <optional>
+        <attribute name="machine">
+          <data type="string">
+            <param name="pattern">[a-zA-Z0-9_\.\-]+</param>
+          </data>
+        </attribute>
+      </optional>
+    </group>
+  </define>
   <define name="osexe">
     <element name="os">
       <element name="type">

src/qemu/qemu_domain.c

@@ -703,6 +703,7 @@ qemuDomainDefPostParse(virDomainDefPtr def,
     bool addImplicitSATA = false;
     bool addPCIRoot = false;
     bool addPCIeRoot = false;
+    bool addDefaultMemballoon = true;
 
     /* check for emulator and create a default one if needed */
     if (!def->emulator &&
@@ -737,6 +738,7 @@ qemuDomainDefPostParse(virDomainDefPtr def,
 
     case VIR_ARCH_ARMV7L:
        addDefaultUSB = false;
+       addDefaultMemballoon = false;
        break;
 
     case VIR_ARCH_ALPHA:
@@ -785,7 +787,7 @@ qemuDomainDefPostParse(virDomainDefPtr def,
         }
     }
 
-    if (!def->memballoon) {
+    if (addDefaultMemballoon && !def->memballoon) {
         virDomainMemballoonDefPtr memballoon;
         if (VIR_ALLOC(memballoon) < 0)
             return -1;

tests/qemuxml2argvdata/qemuxml2argv-arm-vexpressa9-nodevs.args

@@ -0,0 +1,5 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-arm -S -M vexpress-a9 -m 1024 -smp 1 -nographic \
+-nodefconfig -nodefaults -monitor unix:/tmp/test-monitor,server,nowait \
+-boot c -kernel /arm.kernel -initrd /arm.initrd \
+-append console=ttyAMA0,115200n8 -dtb /arm.dtb -usb

tests/qemuxml2argvdata/qemuxml2argv-arm-vexpressa9-nodevs.xml

@@ -0,0 +1,26 @@
+<domain type="qemu">
+  <name>armtest</name>
+  <uuid>496d7ea8-9739-544b-4ebd-ef08be936e6a</uuid>
+  <memory>1048576</memory>
+  <currentMemory>1048576</currentMemory>
+  <vcpu>1</vcpu>
+  <os>
+    <type arch="armv7l" machine="vexpress-a9">hvm</type>
+    <kernel>/arm.kernel</kernel>
+    <initrd>/arm.initrd</initrd>
+    <dtb>/arm.dtb</dtb>
+    <cmdline>console=ttyAMA0,115200n8</cmdline>
+  </os>
+  <features>
+    <acpi/>
+    <apic/>
+    <pae/>
+  </features>
+  <clock offset="utc"/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>restart</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-arm</emulator>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1061,6 +1061,9 @@ mymain(void)
             QEMU_CAPS_VGA_QXL, QEMU_CAPS_DEVICE_QXL,
             QEMU_CAPS_Q35_PCI_HOLE64_SIZE);
 
+    DO_TEST("arm-vexpressa9-nodevs",
+            QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG, QEMU_CAPS_DTB);
+
     virObjectUnref(driver.config);
     virObjectUnref(driver.caps);
     virObjectUnref(driver.xmlopt);

tests/testutilsqemu.c

@@ -145,6 +145,36 @@ error:
     return -1;
 }
 
+static int testQemuAddArmGuest(virCapsPtr caps)
+{
+    static const char *machines[] = { "vexpress-a9",
+                                      "vexpress-a15",
+                                      "versatilepb" };
+    virCapsGuestMachinePtr *capsmachines = NULL;
+    virCapsGuestPtr guest;
+
+    capsmachines = virCapabilitiesAllocMachines(machines,
+                                                ARRAY_CARDINALITY(machines));
+    if (!capsmachines)
+        goto error;
+
+    guest = virCapabilitiesAddGuest(caps, "hvm", VIR_ARCH_ARMV7L,
+                                    "/usr/bin/qemu-system-arm", NULL,
+                                    ARRAY_CARDINALITY(machines),
+                                    capsmachines);
+    if (!guest)
+        goto error;
+
+    if (!virCapabilitiesAddGuestDomain(guest, "qemu", NULL, NULL, 0, NULL))
+        goto error;
+
+    return 0;
+
+error:
+    virCapabilitiesFreeMachines(capsmachines, ARRAY_CARDINALITY(machines));
+    return -1;
+}
+
 
 virCapsPtr testQemuCapsInit(void) {
     virCapsPtr caps;
@@ -270,6 +300,9 @@ virCapsPtr testQemuCapsInit(void) {
     if (testQemuAddS390Guest(caps))
         goto cleanup;
 
+    if (testQemuAddArmGuest(caps))
+        goto cleanup;
+
     if (virTestGetDebug()) {
         char *caps_str;