Taint domains configured with cpu mode=host-passthrough

There are several reasons for doing this:

- the CPU specification is out of libvirt's control so we cannot
  guarantee stable guest ABI
- not every feature of a CPU may actually work as expected when
  advertised directly to a guest
- migration between two machines with exactly the same CPU may work but
  no guarantees can be made
- this mode is not supported and its use is at one's own risk

src/conf/domain_conf.c

@@ -75,7 +75,8 @@ VIR_ENUM_IMPL(virDomainTaint, VIR_DOMAIN_TAINT_LAST,
               "high-privileges",
               "shell-scripts",
               "disk-probing",
-              "external-launch");
+              "external-launch",
+              "host-cpu");
 
 VIR_ENUM_IMPL(virDomainVirt, VIR_DOMAIN_VIRT_LAST,
               "qemu",

src/conf/domain_conf.h

@@ -1524,6 +1524,7 @@ enum virDomainTaintFlags {
     VIR_DOMAIN_TAINT_SHELL_SCRIPTS,    /* Network configuration using opaque shell scripts */
     VIR_DOMAIN_TAINT_DISK_PROBING,     /* Relying on potentially unsafe disk format probing */
     VIR_DOMAIN_TAINT_EXTERNAL_LAUNCH,  /* Externally launched guest domain */
+    VIR_DOMAIN_TAINT_HOST_CPU,         /* Host CPU passthrough in use */
 
     VIR_DOMAIN_TAINT_LAST
 };

src/qemu/qemu_domain.c

@@ -1143,6 +1143,9 @@ void qemuDomainObjCheckTaint(struct qemud_driver *driver,
             qemuDomainObjTaint(driver, obj, VIR_DOMAIN_TAINT_CUSTOM_ARGV, logFD);
     }
 
+    if (obj->def->cpu && obj->def->cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH)
+        qemuDomainObjTaint(driver, obj, VIR_DOMAIN_TAINT_HOST_CPU, logFD);
+
     for (i = 0 ; i < obj->def->ndisks ; i++)
         qemuDomainObjCheckDiskTaint(driver, obj, obj->def->disks[i], logFD);