kernel32: Reimplement GetMaximumProcessorGroupCount on top of GetLogicalProcessorInformationEx.

dlls/kernel32/process.c

@@ -702,8 +702,24 @@ DWORD WINAPI GetMaximumProcessorCount(WORD group)
  */
 WORD WINAPI GetMaximumProcessorGroupCount(void)
 {
-    FIXME("semi-stub, always returning 1\n");
-    return 1;
+    WORD groups;
+    DWORD size = 0;
+    SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX *info;
+
+    TRACE("()\n");
+
+    if (!GetLogicalProcessorInformationEx(RelationGroup, NULL, &size)) return 0;
+    if (!(info = HeapAlloc(GetProcessHeap(), 0, size))) return 0;
+    if (!GetLogicalProcessorInformationEx(RelationGroup, info, &size))
+    {
+        HeapFree(GetProcessHeap(), 0, info);
+        return 0;
+    }
+
+    groups = info->Group.MaximumGroupCount;
+
+    HeapFree(GetProcessHeap(), 0, info);
+    return groups;
 }
 
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