perf kvm: Add live mode

perf kvm stat currently requires back to back record and report commands
to see stats. e.g,.

  perf kvm stat record -p $pid -- sleep 1
  perf kvm stat report

This is inconvenvient for on box monitoring of a VM. This patch
introduces a 'live' mode that in effect combines the record plus report
into one command. e.g., to monitor a single VM:

  perf kvm stat live -p $pid

or all VMs:

  perf kvm stat live

Same stats options for the record+report path work with the live mode.
Display rate defaults to 1 second and can be changed using the -d
option.

v4:
- address comments from Xiao -- verify_vcpu check should not look at
  processors on line for the host, prune configurable options.
- set attr->{mmap,comm,task} to 0 - don't need task events so trim events
  we have to deal with
- better control of time for queue event flushing to reduce frequency of
  "Timestamp below last timeslice flush" failures.

v3:
updated to use existing tracepoint parsing code

v2:
removed ABSTIME arg from timerfd_settime as mentioned by Namhyung
only call perf_kvm__handle_stdin when poll returns activity.

Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1375753297-69645-3-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 633 insertions, 26 deletions

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 7d14a3a45401..29bfca78613e 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -2,6 +2,7 @@
 #include "perf.h"
 
 #include "util/evsel.h"
+#include "util/evlist.h"
 #include "util/util.h"
 #include "util/cache.h"
 #include "util/symbol.h"
@@ -15,9 +16,12 @@
 #include <lk/debugfs.h>
 #include "util/tool.h"
 #include "util/stat.h"
+#include "util/top.h"
 
 #include <sys/prctl.h>
+#include <sys/timerfd.h>
 
+#include <termios.h>
 #include <semaphore.h>
 #include <pthread.h>
 #include <math.h>
@@ -82,6 +86,8 @@ struct exit_reasons_table {
 
 struct perf_kvm_stat {
         struct perf_tool    tool;
+        struct perf_record_opts opts;
+        struct perf_evlist  *evlist;
         struct perf_session *session;
 
         const char *file_name;
@@ -96,10 +102,16 @@ struct perf_kvm_stat {
         struct kvm_events_ops *events_ops;
         key_cmp_fun compare;
         struct list_head kvm_events_cache[EVENTS_CACHE_SIZE];
+
         u64 total_time;
         u64 total_count;
+        u64 lost_events;
 
         struct rb_root result;
+
+        int timerfd;
+        unsigned int display_time;
+        bool live;
 };
 
 
@@ -320,6 +332,23 @@ static void init_kvm_event_record(struct perf_kvm_stat *kvm)
                 INIT_LIST_HEAD(&kvm->kvm_events_cache[i]);
 }
 
+static void clear_events_cache_stats(struct list_head *kvm_events_cache)
+{
+        struct list_head *head;
+        struct kvm_event *event;
+        unsigned int i;
+
+        for (i = 0; i < EVENTS_CACHE_SIZE; i++) {
+                head = &kvm_events_cache[i];
+                list_for_each_entry(event, head, hash_entry) {
+                        /* reset stats for event */
+                        memset(&event->total, 0, sizeof(event->total));
+                        memset(event->vcpu, 0,
+                               event->max_vcpu * sizeof(*event->vcpu));
+                }
+        }
+}
+
 static int kvm_events_hash_fn(u64 key)
 {
         return key & (EVENTS_CACHE_SIZE - 1);
@@ -472,7 +501,11 @@ static bool handle_end_event(struct perf_kvm_stat *kvm,
         vcpu_record->last_event = NULL;
         vcpu_record->start_time = 0;
 
-        BUG_ON(timestamp < time_begin);
+        /* seems to happen once in a while during live mode */
+        if (timestamp < time_begin) {
+                pr_debug("End time before begin time; skipping event.\n");
+                return true;
+        }
 
         time_diff = timestamp - time_begin;
         return update_kvm_event(event, vcpu, time_diff);
@@ -639,24 +672,56 @@ static struct kvm_event *pop_from_result(struct rb_root *result)
         return container_of(node, struct kvm_event, rb);
 }
 
-static void print_vcpu_info(int vcpu)
+static void print_vcpu_info(struct perf_kvm_stat *kvm)
 {
+        int vcpu = kvm->trace_vcpu;
+
         pr_info("Analyze events for ");
 
+        if (kvm->live) {
+                if (kvm->opts.target.system_wide)
+                        pr_info("all VMs, ");
+                else if (kvm->opts.target.pid)
+                        pr_info("pid(s) %s, ", kvm->opts.target.pid);
+                else
+                        pr_info("dazed and confused on what is monitored, ");
+        }
+
         if (vcpu == -1)
                 pr_info("all VCPUs:\n\n");
         else
                 pr_info("VCPU %d:\n\n", vcpu);
 }
 
+static void show_timeofday(void)
+{
+        char date[64];
+        struct timeval tv;
+        struct tm ltime;
+
+        gettimeofday(&tv, NULL);
+        if (localtime_r(&tv.tv_sec, &ltime)) {
+                strftime(date, sizeof(date), "%H:%M:%S", &ltime);
+                pr_info("%s.%06ld", date, tv.tv_usec);
+        } else
+                pr_info("00:00:00.000000");
+
+        return;
+}
+
 static void print_result(struct perf_kvm_stat *kvm)
 {
         char decode[20];
         struct kvm_event *event;
         int vcpu = kvm->trace_vcpu;
 
+        if (kvm->live) {
+                puts(CONSOLE_CLEAR);
+                show_timeofday();
+        }
+
         pr_info("\n\n");
-        print_vcpu_info(vcpu);
+        print_vcpu_info(kvm);
         pr_info("%20s ", kvm->events_ops->name);
         pr_info("%10s ", "Samples");
         pr_info("%9s ", "Samples%");
@@ -683,6 +748,20 @@ static void print_result(struct perf_kvm_stat *kvm)
 
         pr_info("\nTotal Samples:%" PRIu64 ", Total events handled time:%.2fus.\n\n",
                 kvm->total_count, kvm->total_time / 1e3);
+
+        if (kvm->lost_events)
+                pr_info("\nLost events: %" PRIu64 "\n\n", kvm->lost_events);
+}
+
+static int process_lost_event(struct perf_tool *tool,
+                              union perf_event *event __maybe_unused,
+                              struct perf_sample *sample __maybe_unused,
+                              struct machine *machine __maybe_unused)
+{
+        struct perf_kvm_stat *kvm = container_of(tool, struct perf_kvm_stat, tool);
+
+        kvm->lost_events++;
+        return 0;
 }
 
 static int process_sample_event(struct perf_tool *tool,
@@ -707,10 +786,20 @@ static int process_sample_event(struct perf_tool *tool,
         return 0;
 }
 
-static int get_cpu_isa(struct perf_session *session)
+static int cpu_isa_config(struct perf_kvm_stat *kvm)
 {
-        char *cpuid = session->header.env.cpuid;
-        int isa;
+        char buf[64], *cpuid;
+        int err, isa;
+
+        if (kvm->live) {
+                err = get_cpuid(buf, sizeof(buf));
+                if (err != 0) {
+                        pr_err("Failed to look up CPU type (Intel or AMD)\n");
+                        return err;
+                }
+                cpuid = buf;
+        } else
+                cpuid = kvm->session->header.env.cpuid;
 
         if (strstr(cpuid, "Intel"))
                 isa = 1;
@@ -718,10 +807,361 @@ static int get_cpu_isa(struct perf_session *session)
                 isa = 0;
         else {
                 pr_err("CPU %s is not supported.\n", cpuid);
-                isa = -ENOTSUP;
+                return -ENOTSUP;
+        }
+
+        if (isa == 1) {
+                kvm->exit_reasons = vmx_exit_reasons;
+                kvm->exit_reasons_size = ARRAY_SIZE(vmx_exit_reasons);
+                kvm->exit_reasons_isa = "VMX";
+        }
+
+        return 0;
+}
+
+static bool verify_vcpu(int vcpu)
+{
+        if (vcpu != -1 && vcpu < 0) {
+                pr_err("Invalid vcpu:%d.\n", vcpu);
+                return false;
+        }
+
+        return true;
+}
+
+/* keeping the max events to a modest level to keep
+ * the processing of samples per mmap smooth.
+ */
+#define PERF_KVM__MAX_EVENTS_PER_MMAP  25
+
+static s64 perf_kvm__mmap_read_idx(struct perf_kvm_stat *kvm, int idx,
+                                   u64 *mmap_time)
+{
+        union perf_event *event;
+        struct perf_sample sample;
+        s64 n = 0;
+        int err;
+
+        *mmap_time = ULLONG_MAX;
+        while ((event = perf_evlist__mmap_read(kvm->evlist, idx)) != NULL) {
+                err = perf_evlist__parse_sample(kvm->evlist, event, &sample);
+                if (err) {
+                        pr_err("Failed to parse sample\n");
+                        return -1;
+                }
+
+                err = perf_session_queue_event(kvm->session, event, &sample, 0);
+                if (err) {
+                        pr_err("Failed to enqueue sample: %d\n", err);
+                        return -1;
+                }
+
+                /* save time stamp of our first sample for this mmap */
+                if (n == 0)
+                        *mmap_time = sample.time;
+
+                /* limit events per mmap handled all at once */
+                n++;
+                if (n == PERF_KVM__MAX_EVENTS_PER_MMAP)
+                        break;
+        }
+
+        return n;
+}
+
+static int perf_kvm__mmap_read(struct perf_kvm_stat *kvm)
+{
+        int i, err, throttled = 0;
+        s64 n, ntotal = 0;
+        u64 flush_time = ULLONG_MAX, mmap_time;
+
+        for (i = 0; i < kvm->evlist->nr_mmaps; i++) {
+                n = perf_kvm__mmap_read_idx(kvm, i, &mmap_time);
+                if (n < 0)
+                        return -1;
+
+                /* flush time is going to be the minimum of all the individual
+                 * mmap times. Essentially, we flush all the samples queued up
+                 * from the last pass under our minimal start time -- that leaves
+                 * a very small race for samples to come in with a lower timestamp.
+                 * The ioctl to return the perf_clock timestamp should close the
+                 * race entirely.
+                 */
+                if (mmap_time < flush_time)
+                        flush_time = mmap_time;
+
+                ntotal += n;
+                if (n == PERF_KVM__MAX_EVENTS_PER_MMAP)
+                        throttled = 1;
+        }
+
+        /* flush queue after each round in which we processed events */
+        if (ntotal) {
+                kvm->session->ordered_samples.next_flush = flush_time;
+                err = kvm->tool.finished_round(&kvm->tool, NULL, kvm->session);
+                if (err) {
+                        if (kvm->lost_events)
+                                pr_info("\nLost events: %" PRIu64 "\n\n",
+                                        kvm->lost_events);
+                        return err;
+                }
+        }
+
+        return throttled;
+}
+
+static volatile int done;
+
+static void sig_handler(int sig __maybe_unused)
+{
+        done = 1;
+}
+
+static int perf_kvm__timerfd_create(struct perf_kvm_stat *kvm)
+{
+        struct itimerspec new_value;
+        int rc = -1;
+
+        kvm->timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
+        if (kvm->timerfd < 0) {
+                pr_err("timerfd_create failed\n");
+                goto out;
+        }
+
+        new_value.it_value.tv_sec = kvm->display_time;
+        new_value.it_value.tv_nsec = 0;
+        new_value.it_interval.tv_sec = kvm->display_time;
+        new_value.it_interval.tv_nsec = 0;
+
+        if (timerfd_settime(kvm->timerfd, 0, &new_value, NULL) != 0) {
+                pr_err("timerfd_settime failed: %d\n", errno);
+                close(kvm->timerfd);
+                goto out;
+        }
+
+        rc = 0;
+out:
+        return rc;
+}
+
+static int perf_kvm__handle_timerfd(struct perf_kvm_stat *kvm)
+{
+        uint64_t c;
+        int rc;
+
+        rc = read(kvm->timerfd, &c, sizeof(uint64_t));
+        if (rc < 0) {
+                if (errno == EAGAIN)
+                        return 0;
+
+                pr_err("Failed to read timer fd: %d\n", errno);
+                return -1;
+        }
+
+        if (rc != sizeof(uint64_t)) {
+                pr_err("Error reading timer fd - invalid size returned\n");
+                return -1;
+        }
+
+        if (c != 1)
+                pr_debug("Missed timer beats: %" PRIu64 "\n", c-1);
+
+        /* update display */
+        sort_result(kvm);
+        print_result(kvm);
+
+        /* reset counts */
+        clear_events_cache_stats(kvm->kvm_events_cache);
+        kvm->total_count = 0;
+        kvm->total_time = 0;
+        kvm->lost_events = 0;
+
+        return 0;
+}
+
+static int fd_set_nonblock(int fd)
+{
+        long arg = 0;
+
+        arg = fcntl(fd, F_GETFL);
+        if (arg < 0) {
+                pr_err("Failed to get current flags for fd %d\n", fd);
+                return -1;
+        }
+
+        if (fcntl(fd, F_SETFL, arg | O_NONBLOCK) < 0) {
+                pr_err("Failed to set non-block option on fd %d\n", fd);
+                return -1;
+        }
+
+        return 0;
+}
+
+static
+int perf_kvm__handle_stdin(struct termios *tc_now, struct termios *tc_save)
+{
+        int c;
+
+        tcsetattr(0, TCSANOW, tc_now);
+        c = getc(stdin);
+        tcsetattr(0, TCSAFLUSH, tc_save);
+
+        if (c == 'q')
+                return 1;
+
+        return 0;
+}
+
+static int kvm_events_live_report(struct perf_kvm_stat *kvm)
+{
+        struct pollfd *pollfds = NULL;
+        int nr_fds, nr_stdin, ret, err = -EINVAL;
+        struct termios tc, save;
+
+        /* live flag must be set first */
+        kvm->live = true;
+
+        ret = cpu_isa_config(kvm);
+        if (ret < 0)
+                return ret;
+
+        if (!verify_vcpu(kvm->trace_vcpu) ||
+            !select_key(kvm) ||
+            !register_kvm_events_ops(kvm)) {
+                goto out;
+        }
+
+        init_kvm_event_record(kvm);
+
+        tcgetattr(0, &save);
+        tc = save;
+        tc.c_lflag &= ~(ICANON | ECHO);
+        tc.c_cc[VMIN] = 0;
+        tc.c_cc[VTIME] = 0;
+
+        signal(SIGINT, sig_handler);
+        signal(SIGTERM, sig_handler);
+
+        /* copy pollfds -- need to add timerfd and stdin */
+        nr_fds = kvm->evlist->nr_fds;
+        pollfds = zalloc(sizeof(struct pollfd) * (nr_fds + 2));
+        if (!pollfds) {
+                err = -ENOMEM;
+                goto out;
+        }
+        memcpy(pollfds, kvm->evlist->pollfd,
+                sizeof(struct pollfd) * kvm->evlist->nr_fds);
+
+        /* add timer fd */
+        if (perf_kvm__timerfd_create(kvm) < 0) {
+                err = -1;
+                goto out;
+        }
+
+        pollfds[nr_fds].fd = kvm->timerfd;
+        pollfds[nr_fds].events = POLLIN;
+        nr_fds++;
+
+        pollfds[nr_fds].fd = fileno(stdin);
+        pollfds[nr_fds].events = POLLIN;
+        nr_stdin = nr_fds;
+        nr_fds++;
+        if (fd_set_nonblock(fileno(stdin)) != 0)
+                goto out;
+
+        /* everything is good - enable the events and process */
+        perf_evlist__enable(kvm->evlist);
+
+        while (!done) {
+                int rc;
+
+                rc = perf_kvm__mmap_read(kvm);
+                if (rc < 0)
+                        break;
+
+                err = perf_kvm__handle_timerfd(kvm);
+                if (err)
+                        goto out;
+
+                if (pollfds[nr_stdin].revents & POLLIN)
+                        done = perf_kvm__handle_stdin(&tc, &save);
+
+                if (!rc && !done)
+                        err = poll(pollfds, nr_fds, 100);
+        }
+
+        perf_evlist__disable(kvm->evlist);
+
+        if (err == 0) {
+                sort_result(kvm);
+                print_result(kvm);
+        }
+
+out:
+        if (kvm->timerfd >= 0)
+                close(kvm->timerfd);
+
+        if (pollfds)
+                free(pollfds);
+
+        return err;
+}
+
+static int kvm_live_open_events(struct perf_kvm_stat *kvm)
+{
+        int err, rc = -1;
+        struct perf_evsel *pos;
+        struct perf_evlist *evlist = kvm->evlist;
+
+        perf_evlist__config(evlist, &kvm->opts);
+
+        /*
+         * Note: exclude_{guest,host} do not apply here.
+         *       This command processes KVM tracepoints from host only
+         */
+        list_for_each_entry(pos, &evlist->entries, node) {
+                struct perf_event_attr *attr = &pos->attr;
+
+                /* make sure these *are* set */
+                attr->sample_type |= PERF_SAMPLE_TID;
+                attr->sample_type |= PERF_SAMPLE_TIME;
+                attr->sample_type |= PERF_SAMPLE_CPU;
+                attr->sample_type |= PERF_SAMPLE_RAW;
+                /* make sure these are *not*; want as small a sample as possible */
+                attr->sample_type &= ~PERF_SAMPLE_PERIOD;
+                attr->sample_type &= ~PERF_SAMPLE_IP;
+                attr->sample_type &= ~PERF_SAMPLE_CALLCHAIN;
+                attr->sample_type &= ~PERF_SAMPLE_ADDR;
+                attr->sample_type &= ~PERF_SAMPLE_READ;
+                attr->mmap = 0;
+                attr->comm = 0;
+                attr->task = 0;
+
+                attr->sample_period = 1;
+
+                attr->watermark = 0;
+                attr->wakeup_events = 1000;
+
+                /* will enable all once we are ready */
+                attr->disabled = 1;
+        }
+
+        err = perf_evlist__open(evlist);
+        if (err < 0) {
+                printf("Couldn't create the events: %s\n", strerror(errno));
+                goto out;
         }
 
-        return isa;
+        if (perf_evlist__mmap(evlist, kvm->opts.mmap_pages, false) < 0) {
+                ui__error("Failed to mmap the events: %s\n", strerror(errno));
+                perf_evlist__close(evlist);
+                goto out;
+        }
+
+        rc = 0;
+
+out:
+        return rc;
 }
 
 static int read_events(struct perf_kvm_stat *kvm)
@@ -749,30 +1189,13 @@ static int read_events(struct perf_kvm_stat *kvm)
          * Do not use 'isa' recorded in kvm_exit tracepoint since it is not
          * traced in the old kernel.
          */
-        ret = get_cpu_isa(kvm->session);
-
+        ret = cpu_isa_config(kvm);
         if (ret < 0)
                 return ret;
 
-        if (ret == 1) {
-                kvm->exit_reasons = vmx_exit_reasons;
-                kvm->exit_reasons_size = ARRAY_SIZE(vmx_exit_reasons);
-                kvm->exit_reasons_isa = "VMX";
-        }
-
         return perf_session__process_events(kvm->session, &kvm->tool);
 }
 
-static bool verify_vcpu(int vcpu)
-{
-        if (vcpu != -1 && vcpu < 0) {
-                pr_err("Invalid vcpu:%d.\n", vcpu);
-                return false;
-        }
-
-        return true;
-}
-
 static int kvm_events_report_vcpu(struct perf_kvm_stat *kvm)
 {
         int ret = -EINVAL;
@@ -886,6 +1309,186 @@ kvm_events_report(struct perf_kvm_stat *kvm, int argc, const char **argv)
         return kvm_events_report_vcpu(kvm);
 }
 
+static struct perf_evlist *kvm_live_event_list(void)
+{
+        struct perf_evlist *evlist;
+        char *tp, *name, *sys;
+        unsigned int j;
+        int err = -1;
+
+        evlist = perf_evlist__new();
+        if (evlist == NULL)
+                return NULL;
+
+        for (j = 0; j < ARRAY_SIZE(kvm_events_tp); j++) {
+
+                tp = strdup(kvm_events_tp[j]);
+                if (tp == NULL)
+                        goto out;
+
+                /* split tracepoint into subsystem and name */
+                sys = tp;
+                name = strchr(tp, ':');
+                if (name == NULL) {
+                        pr_err("Error parsing %s tracepoint: subsystem delimiter not found\n",
+                                kvm_events_tp[j]);
+                        free(tp);
+                        goto out;
+                }
+                *name = '\0';
+                name++;
+
+                if (perf_evlist__add_newtp(evlist, sys, name, NULL)) {
+                        pr_err("Failed to add %s tracepoint to the list\n", kvm_events_tp[j]);
+                        free(tp);
+                        goto out;
+                }
+
+                free(tp);
+        }
+
+        err = 0;
+
+out:
+        if (err) {
+                perf_evlist__delete(evlist);
+                evlist = NULL;
+        }
+
+        return evlist;
+}
+
+static int kvm_events_live(struct perf_kvm_stat *kvm,
+                           int argc, const char **argv)
+{
+        char errbuf[BUFSIZ];
+        int err;
+
+        const struct option live_options[] = {
+                OPT_STRING('p', "pid", &kvm->opts.target.pid, "pid",
+                        "record events on existing process id"),
+                OPT_UINTEGER('m', "mmap-pages", &kvm->opts.mmap_pages,
+                        "number of mmap data pages"),
+                OPT_INCR('v', "verbose", &verbose,
+                        "be more verbose (show counter open errors, etc)"),
+                OPT_BOOLEAN('a', "all-cpus", &kvm->opts.target.system_wide,
+                        "system-wide collection from all CPUs"),
+                OPT_UINTEGER('d', "display", &kvm->display_time,
+                        "time in seconds between display updates"),
+                OPT_STRING(0, "event", &kvm->report_event, "report event",
+                        "event for reporting: vmexit, mmio, ioport"),
+                OPT_INTEGER(0, "vcpu", &kvm->trace_vcpu,
+                        "vcpu id to report"),
+                OPT_STRING('k', "key", &kvm->sort_key, "sort-key",
+                        "key for sorting: sample(sort by samples number)"
+                        " time (sort by avg time)"),
+                OPT_END()
+        };
+        const char * const live_usage[] = {
+                "perf kvm stat live [<options>]",
+                NULL
+        };
+
+
+        /* event handling */
+        kvm->tool.sample = process_sample_event;
+        kvm->tool.comm   = perf_event__process_comm;
+        kvm->tool.exit   = perf_event__process_exit;
+        kvm->tool.fork   = perf_event__process_fork;
+        kvm->tool.lost   = process_lost_event;
+        kvm->tool.ordered_samples = true;
+        perf_tool__fill_defaults(&kvm->tool);
+
+        /* set defaults */
+        kvm->display_time = 1;
+        kvm->opts.user_interval = 1;
+        kvm->opts.mmap_pages = 512;
+        kvm->opts.target.uses_mmap = false;
+        kvm->opts.target.uid_str = NULL;
+        kvm->opts.target.uid = UINT_MAX;
+
+        symbol__init();
+        disable_buildid_cache();
+
+        use_browser = 0;
+        setup_browser(false);
+
+        if (argc) {
+                argc = parse_options(argc, argv, live_options,
+                                     live_usage, 0);
+                if (argc)
+                        usage_with_options(live_usage, live_options);
+        }
+
+        /*
+         * target related setups
+         */
+        err = perf_target__validate(&kvm->opts.target);
+        if (err) {
+                perf_target__strerror(&kvm->opts.target, err, errbuf, BUFSIZ);
+                ui__warning("%s", errbuf);
+        }
+
+        if (perf_target__none(&kvm->opts.target))
+                kvm->opts.target.system_wide = true;
+
+
+        /*
+         * generate the event list
+         */
+        kvm->evlist = kvm_live_event_list();
+        if (kvm->evlist == NULL) {
+                err = -1;
+                goto out;
+        }
+
+        symbol_conf.nr_events = kvm->evlist->nr_entries;
+
+        if (perf_evlist__create_maps(kvm->evlist, &kvm->opts.target) < 0)
+                usage_with_options(live_usage, live_options);
+
+        /*
+         * perf session
+         */
+        kvm->session = perf_session__new(NULL, O_WRONLY, false, false, &kvm->tool);
+        if (kvm->session == NULL) {
+                err = -ENOMEM;
+                goto out;
+        }
+        kvm->session->evlist = kvm->evlist;
+        perf_session__set_id_hdr_size(kvm->session);
+
+
+        if (perf_target__has_task(&kvm->opts.target))
+                perf_event__synthesize_thread_map(&kvm->tool,
+                                                  kvm->evlist->threads,
+                                                  perf_event__process,
+                                                  &kvm->session->machines.host);
+        else
+                perf_event__synthesize_threads(&kvm->tool, perf_event__process,
+                                               &kvm->session->machines.host);
+
+
+        err = kvm_live_open_events(kvm);
+        if (err)
+                goto out;
+
+        err = kvm_events_live_report(kvm);
+
+out:
+        exit_browser(0);
+
+        if (kvm->session)
+                perf_session__delete(kvm->session);
+        kvm->session = NULL;
+        if (kvm->evlist) {
+                perf_evlist__delete_maps(kvm->evlist);
+                perf_evlist__delete(kvm->evlist);
+        }
+
+        return err;
+}
+
 static void print_kvm_stat_usage(void)
 {
         printf("Usage: perf kvm stat <command>\n\n");
@@ -893,6 +1496,7 @@ static void print_kvm_stat_usage(void)
         printf("# Available commands:\n");
         printf("\trecord: record kvm events\n");
         printf("\treport: report statistical data of kvm events\n");
+        printf("\tlive:   live reporting of statistical data of kvm events\n");
 
         printf("\nOtherwise, it is the alias of 'perf stat':\n");
 }
@@ -922,6 +1526,9 @@ static int kvm_cmd_stat(const char *file_name, int argc, const char **argv)
         if (!strncmp(argv[1], "rep", 3))
                 return kvm_events_report(&kvm, argc - 1 , argv + 1);
 
+        if (!strncmp(argv[1], "live", 4))
+                return kvm_events_live(&kvm, argc - 1 , argv + 1);
+
 perf_stat:
         return cmd_stat(argc, argv, NULL);
 }