[Qemu-devel] [PATCH] target/i386: Fixes to the check missing features routine

[Wainer dos Santos Moschetta]

The x86_cpu_class_check_missing_features() returns a list
of unavailable features compared to the host CPU. Currently it may
return empty strings for unamed features as well as duplicated
names.

For example, the qmp "query-cpu-definitions" below shows one empty
string and repeated "mpx" entries:

(...)
{"execute": "query-cpu-definitions"}
(...)
        {
            "name": "Cascadelake-Server",
            "typename": "Cascadelake-Server-x86_64-cpu",
            "unavailable-features": [
                "hle",
                "rtm",
                "mpx",
                "avx512f",
                "avx512dq",
                "rdseed",
                "adx",
                "smap",
                "clflushopt",
                "clwb",
                "intel-pt",
                "avx512cd",
                "avx512bw",
                "avx512vl",
                "pku",
                "",
                "avx512vnni",
                "spec-ctrl",
                "ssbd",
                "3dnowprefetch",
                "xsavec",
                "xgetbv1",
                "mpx",
                "mpx",
                "avx512f",
                "avx512f",
                "avx512f",
                "pku"
            ],
(...)

Signed-off-by: Wainer dos Santos Moschetta <address@hidden>
---
Note: the skipped testcase was used to test fix in my system so it has
assumptions about the host CPU. It's impracticial to change it to allow
running on any system though. Therefore, I am okay on either leave or remove
it. Opinions?
---
 target/i386/cpu.c                   | 12 +++++-
 tests/acceptance/cpu_definitions.py | 61 +++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 tests/acceptance/cpu_definitions.py

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index f81d35e1f9..2502a3adda 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -3615,19 +3615,29 @@ static void 
x86_cpu_class_check_missing_features(X86CPUClass *xcc,
 
     x86_cpu_filter_features(xc);
 
+    /* Uses an auxiliar dictionary to ensure the list of features has not
+       repeated name. */
+    QDict *unique_feats_dict = qdict_new();
+
     for (w = 0; w < FEATURE_WORDS; w++) {
         uint32_t filtered = xc->filtered_features[w];
         int i;
         for (i = 0; i < 32; i++) {
             if (filtered & (1UL << i)) {
+                const char *fname = g_strdup(x86_cpu_feature_name(w, i));
+                if (!fname || qdict_haskey(unique_feats_dict, fname)) {
+                    continue;
+                }
                 strList *new = g_new0(strList, 1);
-                new->value = g_strdup(x86_cpu_feature_name(w, i));
+                new->value = g_strdup(fname);
                 *next = new;
                 next = &new->next;
+                qdict_put_null(unique_feats_dict, new->value);
             }
         }
     }
 
+    g_free(unique_feats_dict);
     object_unref(OBJECT(xc));
 }
 
diff --git a/tests/acceptance/cpu_definitions.py 
b/tests/acceptance/cpu_definitions.py
new file mode 100644
index 0000000000..65cea0427e
--- /dev/null
+++ b/tests/acceptance/cpu_definitions.py
@@ -0,0 +1,61 @@
+# CPU definitions tests.
+#
+# Copyright (c) 2018 Red Hat, Inc.
+#
+# Author:
+#  Wainer dos Santos Moschetta <address@hidden>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or
+# later.  See the COPYING file in the top-level directory.
+
+from avocado import skip
+from avocado_qemu import Test
+
+
+class CPUDefinitions(Test):
+    """
+    Tests for the CPU definitions.
+
+    :avocado: enable
+    :avocado: tags=x86_64
+    """
+    def test_unavailable_features(self):
+        self.vm.add_args("-machine", "q35,accel=kvm")
+        self.vm.launch()
+        cpu_definitions = self.vm.command('query-cpu-definitions')
+        self.assertTrue(len(cpu_definitions) > 0)
+        for cpu_model in cpu_definitions:
+            name = cpu_model.get('name')
+            unavailable_features = cpu_model.get('unavailable-features')
+
+            self.assertNotIn("", unavailable_features,
+                             name + " has unamed feature")
+            self.assertEqual(len(unavailable_features),
+                             len(set(unavailable_features)),
+                             name + " has duplicate feature")
+
+    @skip("Have assumptions about the host CPU")
+    def test_unavailable_features_manual(self):
+        """
+        This test is meant for manual testing only because the list of expected
+        unavailable features depend on the actual host CPU knowledge.
+        """
+        expected_cpu = 'Cascadelake-Server'
+        expected_unavailable_features = ["hle", "rtm", "mpx", "avx512f",
+                                         "avx512dq", "rdseed", "adx", "smap",
+                                         "clflushopt", "clwb", "intel-pt",
+                                         "avx512cd", "avx512bw", "avx512vl",
+                                         "pku", "avx512vnni", "spec-ctrl",
+                                         "ssbd", "3dnowprefetch", "xsavec",
+                                         "xgetbv1"]
+
+        self.vm.add_args("-machine", "q35,accel=kvm")
+        self.vm.launch()
+        cpu_definitions = self.vm.command('query-cpu-definitions')
+        self.assertTrue(len(cpu_definitions) > 0)
+
+        cpus = [cpu_model for cpu_model in cpu_definitions
+                if cpu_model['name'] == expected_cpu]
+        actual_unavailable_features = cpus[0]['unavailable-features']
+        self.assertCountEqual(expected_unavailable_features,
+                              actual_unavailable_features)
-- 
2.19.1