perf kvm: Polish sorting key

Since histograms supports sorting, the tool doesn't need to maintain the
mapping between the sorting keys and the corresponding comparison
callbacks, therefore, this patch removes structure kvm_event_key.

But we still need to validate the sorting key, this patch uses an array
for sorting keys and renames function select_key() to is_valid_key()
to validate the sorting key passed by user.

Signed-off-by: Leo Yan <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-kvm.c

···
 COMPARE_EVENT_KEY(count, stats.n);
 COMPARE_EVENT_KEY(mean, stats.mean);
 
-#define DEF_SORT_NAME_KEY(name, compare_key)				\
-	{ #name, cmp_event_ ## compare_key }
-
-static struct kvm_event_key keys[] = {
-	DEF_SORT_NAME_KEY(sample, count),
-	DEF_SORT_NAME_KEY(time, mean),
-	{ NULL, NULL }
-};
-
 struct kvm_hists {
 	struct hists		hists;
 	struct perf_hpp_list	list;
···
 	return true;
 }
 
-static bool select_key(struct perf_kvm_stat *kvm)
+static bool is_valid_key(struct perf_kvm_stat *kvm)
 {
-	int i;
+	static const char *key_array[] = {
+		"ev_name", "sample", "time", "max_t", "min_t", "mean_t",
+	};
+	unsigned int i;
 
-	for (i = 0; keys[i].name; i++) {
-		if (!strcmp(keys[i].name, kvm->sort_key)) {
-			kvm->compare = keys[i].key;
+	for (i = 0; i < ARRAY_SIZE(key_array); i++)
+		if (!strcmp(key_array[i], kvm->sort_key))
 			return true;
-		}
-	}
 
-	pr_err("Unknown compare key:%s\n", kvm->sort_key);
+	pr_err("Unsupported sort key: %s\n", kvm->sort_key);
 	return false;
 }
 
···
 		return ret;
 
 	if (!verify_vcpu(kvm->trace_vcpu) ||
-	    !select_key(kvm) ||
+	    !is_valid_key(kvm) ||
 	    !register_kvm_events_ops(kvm)) {
 		goto out;
 	}
···
 	if (!verify_vcpu(vcpu))
 		goto exit;
 
-	if (!select_key(kvm))
+	if (!is_valid_key(kvm))
 		goto exit;
 
 	if (!register_kvm_events_ops(kvm))

tools/perf/util/kvm-stat.h

···
 	struct hist_entry he;
 };
 
-typedef int64_t (*key_cmp_fun)(struct kvm_event*, struct kvm_event*, int);
-
-struct kvm_event_key {
-	const char *name;
-	key_cmp_fun key;
-};
-
 struct child_event_ops {
 	void (*get_key)(struct evsel *evsel,
 			struct perf_sample *sample,
···
 	const char *exit_reasons_isa;
 
 	struct kvm_events_ops *events_ops;
-	key_cmp_fun compare;
 
 	u64 total_time;
 	u64 total_count;