vl.c deprecate incorrect CPUs topology

-smp [cpus],sockets/cores/threads[,maxcpus] should describe topology
so that total number of logical CPUs [sockets * cores * threads]
would be equal to [maxcpus], however historically we didn't have
such check in QEMU and it is possible to start VM with an invalid
topology.
Deprecate invalid options combination so we can make sure that
the topology VM started with is always correct in the future.
Users with an invalid sockets/cores/threads/maxcpus values should
fix their CLI to make sure that
   [sockets * cores * threads] == [maxcpus]

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <1536836762-273036-2-git-send-email-imammedo@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[ehabkost: squashed unit test fix]
Message-Id: <20181019215345.521d58d7@igors-macbook-pro.local>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

qemu-deprecated.texi

@@ -86,6 +86,18 @@ for these file types is 'host_cdrom' or 'host_device' as appropriate.
 The @option{name} parameter of the @option{-net} option is a synonym
 for the @option{id} parameter, which should now be used instead.
 
+@subsection -smp (invalid topologies) (since 3.1)
+
+CPU topology properties should describe whole machine topology including
+possible CPUs.
+
+However, historically it was possible to start QEMU with an incorrect topology
+where @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}},
+which could lead to an incorrect topology enumeration by the guest.
+Support for invalid topologies will be removed, the user must ensure
+topologies described with -smp include all possible cpus, i.e.
+  @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
+
 @section QEMU Machine Protocol (QMP) commands
 
 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)

tests/cpu-plug-test.c

@@ -32,12 +32,12 @@ static void test_plug_with_cpu_add(gconstpointer data)
     unsigned int i;
 
     args = g_strdup_printf("-machine %s -cpu %s "
-                           "-smp sockets=%u,cores=%u,threads=%u,maxcpus=%u",
+                           "-smp 1,sockets=%u,cores=%u,threads=%u,maxcpus=%u",
                            s->machine, s->cpu_model,
                            s->sockets, s->cores, s->threads, s->maxcpus);
     qtest_start(args);
 
-    for (i = s->sockets * s->cores * s->threads; i < s->maxcpus; i++) {
+    for (i = 1; i < s->maxcpus; i++) {
         response = qmp("{ 'execute': 'cpu-add',"
                        "  'arguments': { 'id': %d } }", i);
         g_assert(response);
@@ -56,7 +56,7 @@ static void test_plug_without_cpu_add(gconstpointer data)
     QDict *response;
 
     args = g_strdup_printf("-machine %s -cpu %s "
-                           "-smp sockets=%u,cores=%u,threads=%u,maxcpus=%u",
+                           "-smp 1,sockets=%u,cores=%u,threads=%u,maxcpus=%u",
                            s->machine, s->cpu_model,
                            s->sockets, s->cores, s->threads, s->maxcpus);
     qtest_start(args);
@@ -79,12 +79,12 @@ static void test_plug_with_device_add_x86(gconstpointer data)
     unsigned int s, c, t;
 
     args = g_strdup_printf("-machine %s -cpu %s "
-                           "-smp sockets=%u,cores=%u,threads=%u,maxcpus=%u",
+                           "-smp 1,sockets=%u,cores=%u,threads=%u,maxcpus=%u",
                            td->machine, td->cpu_model,
                            td->sockets, td->cores, td->threads, td->maxcpus);
     qtest_start(args);
 
-    for (s = td->sockets; s < td->maxcpus / td->cores / td->threads; s++) {
+    for (s = 1; s < td->sockets; s++) {
         for (c = 0; c < td->cores; c++) {
             for (t = 0; t < td->threads; t++) {
                 char *id = g_strdup_printf("id-%i-%i-%i", s, c, t);
@@ -113,7 +113,7 @@ static void test_plug_with_device_add_coreid(gconstpointer data)
                            td->sockets, td->cores, td->threads, td->maxcpus);
     qtest_start(args);
 
-    for (c = td->cores; c < td->maxcpus / td->sockets / td->threads; c++) {
+    for (c = 1; c < td->cores; c++) {
         char *id = g_strdup_printf("id-%i", c);
         qtest_qmp_device_add(td->device_model, id, "{'core-id':%u}", c);
         g_free(id);
@@ -148,7 +148,7 @@ static void add_pc_test_case(const char *mname)
     data->sockets = 1;
     data->cores = 3;
     data->threads = 2;
-    data->maxcpus = data->sockets * data->cores * data->threads * 2;
+    data->maxcpus = data->sockets * data->cores * data->threads;
     if (g_str_has_suffix(mname, "-1.4") ||
         (strcmp(mname, "pc-1.3") == 0) ||
         (strcmp(mname, "pc-1.2") == 0) ||
@@ -203,7 +203,7 @@ static void add_pseries_test_case(const char *mname)
     data->sockets = 2;
     data->cores = 3;
     data->threads = 1;
-    data->maxcpus = data->sockets * data->cores * data->threads * 2;
+    data->maxcpus = data->sockets * data->cores * data->threads;
 
     path = g_strdup_printf("cpu-plug/%s/device-add/%ux%ux%u&maxcpus=%u",
                            mname, data->sockets, data->cores,
@@ -229,7 +229,7 @@ static void add_s390x_test_case(const char *mname)
     data->sockets = 1;
     data->cores = 3;
     data->threads = 1;
-    data->maxcpus = data->sockets * data->cores * data->threads * 2;
+    data->maxcpus = data->sockets * data->cores * data->threads;
 
     data2 = g_memdup(data, sizeof(PlugTestData));
     data2->machine = g_strdup(data->machine);

vl.c

@@ -1266,6 +1266,13 @@ static void smp_parse(QemuOpts *opts)
             exit(1);
         }
 
+        if (sockets * cores * threads != max_cpus) {
+            warn_report("Invalid CPU topology deprecated: "
+                        "sockets (%u) * cores (%u) * threads (%u) "
+                        "!= maxcpus (%u)",
+                        sockets, cores, threads, max_cpus);
+        }
+
         smp_cpus = cpus;
         smp_cores = cores;
         smp_threads = threads;