qemu: Drop MSR features from host-model with old QEMU

With QEMU versions which lack "unavailable-features" we use CPUID based
detection of features which were enabled or disabled once QEMU starts.
Thus using MSR features with host-model would result in all of them
being marked as disabled in the active domain definition even though
QEMU did not actually disable them.

Let's make sure we add MSR features to host-model only when
"unavailable-features" property is supported by QEMU.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_capabilities.c

@@ -3193,6 +3193,21 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
             goto error;
     }
 
+    if (ARCH_IS_X86(qemuCaps->arch) &&
+        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_UNAVAILABLE_FEATURES)) {
+        if (cpu &&
+            virCPUDefFilterFeatures(cpu, virCPUx86FeatureFilterDropMSR, NULL) < 0)
+            goto error;
+
+        if (migCPU &&
+            virCPUDefFilterFeatures(migCPU, virCPUx86FeatureFilterDropMSR, NULL) < 0)
+            goto error;
+
+        if (fullCPU &&
+            virCPUDefFilterFeatures(fullCPU, virCPUx86FeatureFilterDropMSR, NULL) < 0)
+            goto error;
+    }
+
     virQEMUCapsSetHostModel(qemuCaps, type, cpu, migCPU, fullCPU);
 
  cleanup:

tests/domaincapsschemadata/qemu_3.1.0.x86_64.xml

@@ -42,7 +42,6 @@
       <feature policy='require' name='xsaves'/>
       <feature policy='require' name='pdpe1gb'/>
       <feature policy='require' name='invtsc'/>
-      <feature policy='require' name='skip-l1dfl-vmentry'/>
     </mode>
     <mode name='custom' supported='yes'>
       <model usable='yes'>qemu64</model>

tests/domaincapsschemadata/qemu_4.0.0.x86_64.xml

@@ -42,7 +42,6 @@
       <feature policy='require' name='xsaves'/>
       <feature policy='require' name='pdpe1gb'/>
       <feature policy='require' name='invtsc'/>
-      <feature policy='require' name='skip-l1dfl-vmentry'/>
     </mode>
     <mode name='custom' supported='yes'>
       <model usable='yes'>qemu64</model>