hw/core/machine-smp: Deprecate unsupported "parameter=1" SMP configurations

Currently, it was allowed for users to specify the unsupported
topology parameter as "1". For example, x86 PC machine doesn't
support drawer/book/cluster topology levels, but user could specify
"-smp drawers=1,books=1,clusters=1".

This is meaningless and confusing, so that the support for this kind of
configurations is marked deprecated since 9.0. And report warning
message for such case like:

qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
                    Unsupported clusters parameter mustn't be specified as 1
qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
                    Unsupported books parameter mustn't be specified as 1
qemu-system-x86_64: warning: Deprecated CPU topology (considered invalid):
                    Unsupported drawers parameter mustn't be specified as 1

Users have to ensure that all the topology members described with -smp
are supported by the target machine.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20240308160148.3130837-3-zhao1.liu@linux.intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

docs/about/deprecated.rst

@@ -57,6 +57,20 @@ The ``-p`` option pretends to control the host page size.  However,
 it is not possible to change the host page size, and using the
 option only causes failures.
 
+``-smp`` (Unsupported "parameter=1" SMP configurations) (since 9.0)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Specified CPU topology parameters must be supported by the machine.
+
+In the SMP configuration, users should provide the CPU topology parameters that
+are supported by the target machine.
+
+However, historically it was allowed for users to specify the unsupported
+topology parameter as "1", which is meaningless. So support for this kind of
+configurations (e.g. -smp drawers=1,books=1,clusters=1 for x86 PC machine) is
+marked deprecated since 9.0, users have to ensure that all the topology members
+described with -smp are supported by the target machine.
+
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
 

hw/core/machine-smp.c

@@ -112,30 +112,61 @@ void machine_parse_smp_config(MachineState *ms,
 
     /*
      * If not supported by the machine, a topology parameter must be
-     * omitted or specified equal to 1.
+     * omitted.
      */
-    if (!mc->smp_props.dies_supported && dies > 1) {
-        error_setg(errp, "dies not supported by this machine's CPU topology");
-        return;
-    }
-    if (!mc->smp_props.clusters_supported && clusters > 1) {
-        error_setg(errp, "clusters not supported by this machine's CPU topology");
-        return;
+    if (!mc->smp_props.clusters_supported && config->has_clusters) {
+        if (config->clusters > 1) {
+            error_setg(errp, "clusters not supported by this "
+                       "machine's CPU topology");
+            return;
+        } else {
+            /* Here clusters only equals 1 since we've checked zero case. */
+            warn_report("Deprecated CPU topology (considered invalid): "
+                        "Unsupported clusters parameter mustn't be "
+                        "specified as 1");
+        }
     }
+    clusters = clusters > 0 ? clusters : 1;
 
+    if (!mc->smp_props.dies_supported && config->has_dies) {
+        if (config->dies > 1) {
+            error_setg(errp, "dies not supported by this "
+                       "machine's CPU topology");
+            return;
+        } else {
+            /* Here dies only equals 1 since we've checked zero case. */
+            warn_report("Deprecated CPU topology (considered invalid): "
+                        "Unsupported dies parameter mustn't be "
+                        "specified as 1");
+        }
+    }
     dies = dies > 0 ? dies : 1;
-    clusters = clusters > 0 ? clusters : 1;
 
-    if (!mc->smp_props.books_supported && books > 1) {
-        error_setg(errp, "books not supported by this machine's CPU topology");
-        return;
+    if (!mc->smp_props.books_supported && config->has_books) {
+        if (config->books > 1) {
+            error_setg(errp, "books not supported by this "
+                       "machine's CPU topology");
+            return;
+        } else {
+            /* Here books only equals 1 since we've checked zero case. */
+            warn_report("Deprecated CPU topology (considered invalid): "
+                        "Unsupported books parameter mustn't be "
+                        "specified as 1");
+        }
     }
     books = books > 0 ? books : 1;
 
-    if (!mc->smp_props.drawers_supported && drawers > 1) {
-        error_setg(errp,
-                   "drawers not supported by this machine's CPU topology");
-        return;
+    if (!mc->smp_props.drawers_supported && config->has_drawers) {
+        if (config->drawers > 1) {
+            error_setg(errp, "drawers not supported by this "
+                       "machine's CPU topology");
+            return;
+        } else {
+            /* Here drawers only equals 1 since we've checked zero case. */
+            warn_report("Deprecated CPU topology (considered invalid): "
+                        "Unsupported drawers parameter mustn't be "
+                        "specified as 1");
+        }
     }
     drawers = drawers > 0 ? drawers : 1;