cpu_x86: Fix host-model CPUs on hosts with CMT

Since the introduction of CMT features (commit v1.3.5-461-gf294b83e)
starting a domain with host-model CPU on a host which supports CMT fails
because QEMU complains about unknown 'cmt' feature:

    qemu-system-x86_64: CPU feature cmt not found

https://bugzilla.redhat.com/show_bug.cgi?id=1355857Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/cpu/cpu_x86.c

@@ -2542,12 +2542,16 @@ x86UpdateHostModel(virCPUDefPtr guest,
             goto cleanup;
     }
 
-    /* Remove non-migratable features by default
+    /* Remove non-migratable features and CMT related features which QEMU
+     * knows nothing about.
      * Note: this only works as long as no CPU model contains non-migratable
      * features directly */
     i = 0;
     while (i < guest->nfeatures) {
-        if (x86FeatureIsMigratable(guest->features[i].name, map)) {
+        if (x86FeatureIsMigratable(guest->features[i].name, map) &&
+            STRNEQ(guest->features[i].name, "cmt") &&
+            STRNEQ(guest->features[i].name, "mbm_total") &&
+            STRNEQ(guest->features[i].name, "mbm_local")) {
             i++;
         } else {
             VIR_FREE(guest->features[i].name);

tests/qemuxml2argvdata/qemuxml2argv-cpu-host-model-cmt.args

@@ -9,7 +9,7 @@ QEMU_AUDIO_DRV=none \
 -S \
 -M pc \
 -cpu Haswell,+vme,+ds,+acpi,+ss,+ht,+tm,+pbe,+dtes64,+monitor,+ds_cpl,+vmx,\
-+smx,+est,+tm2,+xtpr,+pdcm,+osxsave,+f16c,+rdrand,+cmt,+pdpe1gb,+abm \
++smx,+est,+tm2,+xtpr,+pdcm,+osxsave,+f16c,+rdrand,+pdpe1gb,+abm \
 -m 214 \
 -smp 6,sockets=6,cores=1,threads=1 \
 -uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \