perf data: Fix perf.data documentation for HEADER_CPU_TOPOLOGY

The 'die' info isn't in the same array as core and socket ids, and we
missed the 'dies' string list, that comes right after the 'core' +
'socket' id variable length array, followed by the VLA for the dies.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: c9cb12c5ba08 ("perf header: Add die information in CPU topology")
Link: https://lkml.kernel.org/n/tip-nubi6mxp2n8ofvlx7ph6k3h6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf.data-file-format.txt

@@ -151,20 +151,35 @@ struct {
 
 	HEADER_CPU_TOPOLOGY = 13,
 
-String lists defining the core and CPU threads topology.
-The string lists are followed by a variable length array
-which contains core_id, die_id (for x86) and socket_id of each cpu.
-The number of entries can be determined by the size of the
-section minus the sizes of both string lists.
-
 struct {
+	/*
+	 * First revision of HEADER_CPU_TOPOLOGY
+	 *
+	 * See 'struct perf_header_string_list' definition earlier
+	 * in this file.
+	 */
+
        struct perf_header_string_list cores; /* Variable length */
        struct perf_header_string_list threads; /* Variable length */
+
+       /*
+        * Second revision of HEADER_CPU_TOPOLOGY, older tools
+        * will not consider what comes next
+        */
+
        struct {
 	      uint32_t core_id;
-	      uint32_t die_id;
 	      uint32_t socket_id;
        } cpus[nr]; /* Variable length records */
+       /* 'nr' comes from previously processed HEADER_NRCPUS's nr_cpu_avail */
+
+        /*
+	 * Third revision of HEADER_CPU_TOPOLOGY, older tools
+	 * will not consider what comes next
+	 */
+
+	struct perf_header_string_list dies; /* Variable length */
+	uint32_t die_id[nr_cpus_avail]; /* from previously processed HEADER_NR_CPUS, VLA */
 };
 
 Example: