Ignore CPU features without a model for host-passthrough

This fixes reverting to snapshots created by older libvirt
and allows libvirt not to lose track of a domain that
has this in its live status XML (such as a domain
restored from managedsave)

https://bugzilla.redhat.com/show_bug.cgi?id=1030793
https://bugzilla.redhat.com/show_bug.cgi?id=1151885

src/conf/cpu_conf.c

@@ -366,6 +366,11 @@ virCPUDefParseXML(xmlNodePtr node,
         goto error;
 
     if (n > 0) {
+        if (!def->model && def->mode == VIR_CPU_MODE_HOST_PASSTHROUGH) {
+            /* silently ignore incorrectly formatted features generated
+             * by older libvirt */
+            goto cleanup;
+        }
         if (!def->model && def->mode != VIR_CPU_MODE_HOST_MODEL) {
             virReportError(VIR_ERR_XML_ERROR, "%s",
                            _("Non-empty feature list specified without "

tests/qemuxml2argvdata/qemuxml2argv-cpu-host-passthrough-features-invalid.args

+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUD\
+IO_DRV=none \
+/usr/bin/qemu \
+-S \
+-M pc \
+-cpu host \
+-m 214 \
+-smp 1 \
+-nographic \
+-monitor unix:/tmp/test-monitor,server,nowait \
+-no-acpi \
+-boot c \
+-usb \
+-hda /dev/HostVG/QEMUGuest1 \
+-net none \
+-serial none \
+-parallel none

tests/qemuxml2argvdata/qemuxml2argv-cpu-host-passthrough-features-invalid.xml

+<domain type='kvm'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <title>A description of the test machine.</title>
+  <description>
+      A test of qemu&apos;s minimal configuration.
+      This test also tests the description and title elements.
+  </description>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static' cpuset='1-4,8-20,525'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <feature policy='require' name='abm'/>
+    <feature policy='require' name='pdpe1gb'/>
+    <feature policy='require' name='rdrand'/>
+    <feature policy='require' name='f16c'/>
+    <feature policy='require' name='osxsave'/>
+    <feature policy='require' name='pdcm'/>
+    <feature policy='require' name='xtpr'/>
+    <feature policy='require' name='tm2'/>
+    <feature policy='require' name='est'/>
+    <feature policy='require' name='smx'/>
+    <feature policy='require' name='vmx'/>
+    <feature policy='require' name='ds_cpl'/>
+    <feature policy='require' name='monitor'/>
+    <feature policy='require' name='dtes64'/>
+    <feature policy='require' name='pbe'/>
+    <feature policy='require' name='tm'/>
+    <feature policy='require' name='ht'/>
+    <feature policy='require' name='ss'/>
+    <feature policy='require' name='acpi'/>
+    <feature policy='require' name='ds'/>
+    <feature policy='require' name='vme'/>
+  </cpu>
+  <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'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1523,6 +1523,7 @@ mymain(void)
     DO_TEST_FAILURE("shmem-small-size", QEMU_CAPS_PCIDEVICE,
                     QEMU_CAPS_DEVICE, QEMU_CAPS_DEVICE_IVSHMEM);
     DO_TEST_PARSE_ERROR("shmem-msi-only", NONE);
+    DO_TEST("cpu-host-passthrough-features-invalid", QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST);
 
     virObjectUnref(driver.config);
     virObjectUnref(driver.caps);