qemu: Report better host-model CPUs in domain caps

One of the main reasons for introducing host-model CPU definition in a
domain capabilities XML was the inability to express disabled features
in a host capabilities XML. That is, when a host CPU is, e.g., Haswell
without x2apic support, host capabilities XML will have to report it as
Westmere + a bunch of additional features., but we really want to use
Haswell - x2apic when creating a host-model CPU.

Unfortunately, I somehow forgot to do the last step and the code would
just copy the CPU definition found in the host capabilities XML. This
changed recently for new QEMU versions which allow us to query host CPU,
but any slightly older QEMU will not benefit from any change I did. This
patch makes sure the right CPU model is filled in the domain
capabilities even with old QEMU.

The issue was reported in
https://bugzilla.redhat.com/show_bug.cgi?id=1426456

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_capabilities.c

@@ -1074,6 +1074,26 @@ virQEMUCapsProbeHostCPU(virCapsPtr caps)
 }
 
 
+virCPUDefPtr
+virQEMUCapsProbeHostCPUForEmulator(virCapsPtr caps,
+                                   virQEMUCapsPtr qemuCaps,
+                                   virDomainVirtType type)
+{
+    size_t nmodels;
+    char **models;
+    virCPUDefPtr cpu;
+
+    if (virQEMUCapsGetCPUDefinitions(qemuCaps, type, &models, &nmodels) < 0)
+        return NULL;
+
+    cpu = virCPUGetHost(caps->host.arch, VIR_CPU_TYPE_GUEST, NULL,
+                        (const char **) models, nmodels);
+
+    virStringListFreeCount(models, nmodels);
+    return cpu;
+}
+
+
 static int
 virQEMUCapsInitPages(virCapsPtr caps)
 {
@@ -3207,6 +3227,7 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
                             virDomainVirtType type)
 {
     virCPUDefPtr cpu = NULL;
+    virCPUDefPtr hostCPU = NULL;
     int rc;
 
     if (!caps || !virQEMUCapsGuestIsNative(caps->host.arch, qemuCaps->arch))
@@ -3223,11 +3244,11 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
     if ((rc = virQEMUCapsInitCPUModel(qemuCaps, type, cpu)) < 0) {
         goto error;
     } else if (rc == 1) {
-        VIR_DEBUG("No host CPU model info from QEMU; using host capabilities");
+        VIR_DEBUG("No host CPU model info from QEMU; probing host CPU directly");
-        if (!caps->host.cpu || !caps->host.cpu->model)
-            goto error;
 
-        if (virCPUDefCopyModelFilter(cpu, caps->host.cpu, true,
+        hostCPU = virQEMUCapsProbeHostCPUForEmulator(caps, qemuCaps, type);
+        if (!hostCPU ||
+            virCPUDefCopyModelFilter(cpu, hostCPU, true,
                                      virQEMUCapsCPUFilterFeatures,
                                      qemuCaps) < 0)
             goto error;
@@ -3238,11 +3259,14 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,
     else
         qemuCaps->tcgCPUModel = cpu;
 
+ cleanup:
+    virCPUDefFree(hostCPU);
     return;
 
  error:
     virCPUDefFree(cpu);
     virResetLastError();
+    goto cleanup;
 }
 
 

src/qemu/qemu_capspriv.h

@@ -87,4 +87,9 @@ void
 virQEMUCapsSetCPUModelInfo(virQEMUCapsPtr qemuCaps,
                            virDomainVirtType type,
                            qemuMonitorCPUModelInfoPtr modelInfo);
+
+virCPUDefPtr
+virQEMUCapsProbeHostCPUForEmulator(virCapsPtr caps,
+                                   virQEMUCapsPtr qemuCaps,
+                                   virDomainVirtType type);
 #endif

tests/Makefile.am

@@ -284,6 +284,7 @@ test_libraries += libqemumonitortestutils.la \
 		qemuxml2xmlmock.la \
 		qemucaps2xmlmock.la \
 		qemucapsprobemock.la \
+		qemucpumock.la \
 		$(NULL)
 endif WITH_QEMU
 
@@ -549,10 +550,16 @@ libqemutestdriver_la_SOURCES =
 libqemutestdriver_la_LDFLAGS = $(QEMULIB_LDFLAGS)
 libqemutestdriver_la_LIBADD = $(qemu_LDADDS)
 
+qemucpumock_la_SOURCES = \
+	qemucpumock.c
+qemucpumock_la_CFLAGS = $(AM_CFLAGS)
+qemucpumock_la_LDFLAGS = $(MOCKLIBS_LDFLAGS)
+qemucpumock_la_LIBADD = $(MOCKLIBS_LIBS)
+
 qemuxml2argvtest_SOURCES = \
 	qemuxml2argvtest.c testutilsqemu.c testutilsqemu.h \
 	testutils.c testutils.h
-qemuxml2argvtest_LDADD = $(qemu_LDADDS) $(LDADDS) $(LIBXML_LIBS)
+qemuxml2argvtest_LDADD = libqemutestdriver.la $(LDADDS) $(LIBXML_LIBS)
 
 qemuxml2argvmock_la_SOURCES = \
 	qemuxml2argvmock.c
@@ -949,7 +956,7 @@ domaincapstest_LDADD = $(LDADDS)
 
 if WITH_QEMU
 domaincapstest_SOURCES += testutilsqemu.c testutilsqemu.h
-domaincapstest_LDADD += $(qemu_LDADDS) $(GNULIB_LIBS)
+domaincapstest_LDADD += libqemutestdriver.la $(GNULIB_LIBS)
 endif WITH_QEMU
 
 if WITH_LIBXL

tests/domaincapstest.c

@@ -491,4 +491,10 @@ mymain(void)
     return ret;
 }
 
+#if WITH_QEMU
+VIRT_TEST_MAIN_PRELOAD(mymain,
+                       abs_builddir "/.libs/domaincapsmock.so",
+                       abs_builddir "/.libs/qemucpumock.so")
+#else
 VIRT_TEST_MAIN_PRELOAD(mymain, abs_builddir "/.libs/domaincapsmock.so")
+#endif

tests/qemucpumock.c

@@ -0,0 +1,35 @@
+/*
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+
+#include "internal.h"
+#include "qemu/qemu_capabilities.h"
+#define __QEMU_CAPSRIV_H_ALLOW__
+#include "qemu/qemu_capspriv.h"
+#undef __QEMU_CAPSRIV_H_ALLOW__
+
+
+virCPUDefPtr
+virQEMUCapsProbeHostCPUForEmulator(virCapsPtr caps,
+                                   virQEMUCapsPtr qemuCaps ATTRIBUTE_UNUSED,
+                                   virDomainVirtType type ATTRIBUTE_UNUSED)
+{
+    if (!caps || !caps->host.cpu || !caps->host.cpu->model)
+        return NULL;
+
+    return virCPUDefCopy(caps->host.cpu);
+}

tests/qemuxml2argvtest.c

@@ -2473,8 +2473,10 @@ mymain(void)
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
 
-VIRT_TEST_MAIN_PRELOAD(mymain, abs_builddir "/.libs/qemuxml2argvmock.so",
+VIRT_TEST_MAIN_PRELOAD(mymain,
-                       abs_builddir "/.libs/virrandommock.so")
+                       abs_builddir "/.libs/qemuxml2argvmock.so",
+                       abs_builddir "/.libs/virrandommock.so",
+                       abs_builddir "/.libs/qemucpumock.so")
 
 #else