contrib/plugins/hotblocks: Allow limit to be set as a command line argument

Also add documentation for this argument. This allows the default of 20
to be overridden, and is helpful for using the hotblocks plugin for
analysis scripts that require collecting data on a larger number of
blocks (e.g. setting limit=0 to dump information on all blocks).

Signed-off-by: Alex Bradbury <asb@igalia.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Link: https://lore.kernel.org/qemu-devel/58281d6e54bcad1802e8d3dc8d8501d54c2a971e.1753857212.git.asb@igalia.com
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>

contrib/plugins/hotblocks.c

@@ -84,7 +84,8 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
     if (sorted_counts) {
         g_string_append_printf(report, "pc, tcount, icount, ecount\n");
 
-        for (i = 0, it = sorted_counts; i < limit && it; i++, it = it->next) {
+        for (i = 0, it = sorted_counts; (limit == 0 || i < limit) && it;
+             i++, it = it->next) {
             ExecCount *rec = (ExecCount *) it->data;
             g_string_append_printf(
                 report, "0x%016"PRIx64", %d, %ld, %"PRIu64"\n",
@@ -170,6 +171,13 @@ int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
                 fprintf(stderr, "boolean argument parsing failed: %s\n", opt);
                 return -1;
             }
+        } else if (g_strcmp0(tokens[0], "limit") == 0) {
+            char *endptr = NULL;
+            limit = g_ascii_strtoull(tokens[1], &endptr, 10);
+            if (endptr == tokens[1] || *endptr != '\0') {
+                fprintf(stderr, "unsigned integer parsing failed: %s\n", opt);
+                return -1;
+            }
         } else {
             fprintf(stderr, "option parsing failed: %s\n", opt);
             return -1;

docs/about/emulation.rst

@@ -473,6 +473,8 @@ Behaviour can be tweaked with the following arguments:
     - Description
   * - inline=true|false
     - Use faster inline addition of a single counter.
+  * - limit=N
+    - The number of blocks to be printed. (Default: N = 20, use 0 for no limit).
 
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