kvm tools: Add 'kvm stat' command

This patch adds 'kvm stat' command that allows retrieving statistics out of
a running guest.

Currently the only supported statistics are memory statistics, available using the
'--memory' parameter.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

builtin-stat.c

@@ -0,0 +1,79 @@
+#include <kvm/util.h>
+#include <kvm/kvm-cmd.h>
+#include <kvm/builtin-stat.h>
+#include <kvm/kvm.h>
+#include <kvm/parse-options.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+static bool mem;
+static bool all;
+static u64 instance_pid;
+static const char *instance_name;
+
+static const char * const stat_usage[] = {
+	"kvm stat [command] [--all] [-n name] [-p pid]",
+	NULL
+};
+
+static const struct option stat_options[] = {
+	OPT_GROUP("Commands options:"),
+	OPT_BOOLEAN('m', "memory", &mem, "Display memory statistics"),
+	OPT_GROUP("Instance options:"),
+	OPT_BOOLEAN('a', "all", &all, "All instances"),
+	OPT_STRING('n', "name", &instance_name, "name", "Instance name"),
+	OPT_U64('p', "pid", &instance_pid, "Instance pid"),
+	OPT_END()
+};
+
+static void parse_stat_options(int argc, const char **argv)
+{
+	while (argc != 0) {
+		argc = parse_options(argc, argv, stat_options, stat_usage,
+				PARSE_OPT_STOP_AT_NON_OPTION);
+		if (argc != 0)
+			kvm_stat_help();
+	}
+}
+
+void kvm_stat_help(void)
+{
+	usage_with_options(stat_usage, stat_options);
+}
+
+static int do_memstat(const char *name, int pid)
+{
+	printf("Sending memstat command to %s, output should be on the targets' terminal.\n", name);
+	return kill(pid, SIGKVMMEMSTAT);
+}
+
+int kvm_cmd_stat(int argc, const char **argv, const char *prefix)
+{
+	parse_stat_options(argc, argv);
+
+	if (!mem)
+		usage_with_options(stat_usage, stat_options);
+
+	if (mem && all)
+		return kvm__enumerate_instances(do_memstat);
+
+	if (instance_name == NULL &&
+	    instance_pid == 0)
+		kvm_stat_help();
+
+	if (instance_name)
+		instance_pid = kvm__get_pid_by_instance(instance_name);
+
+	if (instance_pid <= 0)
+		die("Failed locating instance");
+
+	if (mem) {
+		printf("Sending memstat command to designated instance, output should be on the targets' terminal.\n");
+
+		return kill(instance_pid, SIGKVMMEMSTAT);
+	}
+
+	return 0;
+}