diff mbox series

[v13,08/10] Adding info [tb-list|tb] commands to HMP (WIP)

Message ID 20230529114947.2123652-9-fei2.wu@intel.com (mailing list archive)
State New, archived
Headers show
Series TCG code quality tracking | expand

Commit Message

Wu, Fei May 29, 2023, 11:49 a.m. UTC
From: "Vanderson M. do Rosario" <vandersonmr2@gmail.com>

These commands allow the exploration of TBs generated by the TCG.
Understand which one hotter, with more guest/host instructions... and
examine their guest, host and IR code.

The goal of this command is to allow the dynamic exploration of TCG
behavior and code quality. Therefore, for now, a corresponding QMP
command is not worthwhile.

[AJB: WIP - we still can't be safely sure a translation will succeed]

Example of output:

TB id:1 | phys:0x34d54 virt:0x0000000000034d54 flags:0x0000f0
	| exec:4828932/0 guest inst cov:16.38%
	| trans:1 ints: g:3 op:82 op_opt:34 spills:3
	| h/g (host bytes / guest insts): 90.666664
	| time to gen at 2.4GHz => code:3150.83(ns) IR:712.08(ns)
	| targets: 0x0000000000034d5e (id:11), 0x0000000000034d0d (id:2)

TB id:2 | phys:0x34d0d virt:0x0000000000034d0d flags:0x0000f0
	| exec:4825842/0 guest inst cov:21.82%
	| trans:1 ints: g:4 op:80 op_opt:38 spills:2
	| h/g (host bytes / guest insts): 84.000000
	| time to gen at 2.4GHz => code:3362.92(ns) IR:793.75(ns)
	| targets: 0x0000000000034d19 (id:12), 0x0000000000034d54 (id:1)

TB id:2 | phys:0x34d0d virt:0x0000000000034d0d flags:0x0000f0
	| exec:6956495/0  guest inst cov:21.82%
	| trans:2 ints: g:2 op:40 op_opt:19 spills:1
	| h/g (host bytes / guest insts): 84.000000
	| time to gen at 2.4GHz => code:3130.83(ns) IR:722.50(ns)
	| targets: 0x0000000000034d19 (id:12), 0x0000000000034d54 (id:1)

----------------
IN:
0x00034d0d:  89 de                    movl     %ebx, %esi
0x00034d0f:  26 8b 0e                 movl     %es:(%esi), %ecx
0x00034d12:  26 f6 46 08 80           testb    $0x80, %es:8(%esi)
0x00034d17:  75 3b                    jne      0x34d54

------------------------------

TB id:1 | phys:0x34d54 virt:0x0000000000034d54 flags:0x0000f0
	| exec:5202686/0 guest inst cov:11.28%
	| trans:1 ints: g:3 op:82 op_opt:34 spills:3
	| h/g (host bytes / guest insts): 90.666664
	| time to gen at 2.4GHz => code:2793.75(ns) IR:614.58(ns)
	| targets: 0x0000000000034d5e (id:3), 0x0000000000034d0d (id:2)

TB id:2 | phys:0x34d0d virt:0x0000000000034d0d flags:0x0000f0
	| exec:5199468/0 guest inst cov:15.03%
	| trans:1 ints: g:4 op:80 op_opt:38 spills:2
	| h/g (host bytes / guest insts): 84.000000
	| time to gen at 2.4GHz => code:2958.75(ns) IR:719.58(ns)
	| targets: 0x0000000000034d19 (id:4), 0x0000000000034d54 (id:1)

------------------------------
2 TBs to reach 25% of guest inst exec coverage
Total of guest insts exec: 138346727

------------------------------

Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Vanderson M. do Rosario <vandersonmr2@gmail.com>
Message-Id: <20190829173437.5926-10-vandersonmr2@gmail.com>
[AJB: fix authorship, dropped coverset]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Fei Wu <fei2.wu@intel.com>
---
 accel/tcg/monitor.c          |  54 ++++++
 accel/tcg/tb-stats.c         | 322 +++++++++++++++++++++++++++++++++++
 disas/disas.c                |  26 ++-
 hmp-commands-info.hx         |  16 ++
 include/exec/tb-stats.h      |  33 +++-
 include/monitor/hmp.h        |   2 +
 include/qemu/log-for-trace.h |   6 +-
 include/qemu/log.h           |   2 +
 util/log.c                   |  66 +++++--
 9 files changed, 508 insertions(+), 19 deletions(-)
diff mbox series

Patch

diff --git a/accel/tcg/monitor.c b/accel/tcg/monitor.c
index 2e00f10267..a1780c5920 100644
--- a/accel/tcg/monitor.c
+++ b/accel/tcg/monitor.c
@@ -8,6 +8,7 @@ 
 
 #include "qemu/osdep.h"
 #include "qemu/accel.h"
+#include "qemu/log.h"
 #include "qapi/error.h"
 #include "qapi/type-helpers.h"
 #include "qapi/qapi-commands-machine.h"
@@ -18,6 +19,7 @@ 
 #include "sysemu/cpu-timers.h"
 #include "sysemu/tcg.h"
 #include "exec/tb-stats.h"
+#include "tb-context.h"
 #include "internal.h"
 
 
@@ -132,6 +134,58 @@  void hmp_tbstats(Monitor *mon, const QDict *qdict)
 
 }
 
+void hmp_info_tblist(Monitor *mon, const QDict *qdict)
+{
+    int number_int;
+    const char *sortedby_str = NULL;
+    if (!tcg_enabled()) {
+        error_report("TB information is only available with accel=tcg");
+        return;
+    }
+    if (!tb_ctx.tb_stats.map) {
+        error_report("no TB information recorded");
+        return;
+    }
+
+    number_int = qdict_get_try_int(qdict, "number", 10);
+    sortedby_str = qdict_get_try_str(qdict, "sortedby");
+
+    int sortedby = SORT_BY_HOTNESS;
+    if (sortedby_str == NULL || strcmp(sortedby_str, "hotness") == 0) {
+        sortedby = SORT_BY_HOTNESS;
+    } else if (strcmp(sortedby_str, "hg") == 0) {
+        sortedby = SORT_BY_HG;
+    } else if (strcmp(sortedby_str, "spills") == 0) {
+        sortedby = SORT_BY_SPILLS;
+    } else {
+        error_report("valid sort options are: hotness hg spills");
+        return;
+    }
+
+    dump_tbs_info(number_int, sortedby, true);
+}
+
+void hmp_info_tb(Monitor *mon, const QDict *qdict)
+{
+    const int id = qdict_get_int(qdict, "id");
+    const char *flags = qdict_get_try_str(qdict, "flags");
+    int mask;
+
+    if (!tcg_enabled()) {
+        error_report("TB information is only available with accel=tcg");
+        return;
+    }
+
+    mask = flags ? qemu_str_to_log_mask(flags) : CPU_LOG_TB_IN_ASM;
+
+    if (!mask) {
+        error_report("Unable to parse log flags, see 'help log'");
+        return;
+    }
+
+    dump_tb_info(id, mask, true);
+}
+
 HumanReadableText *qmp_x_query_profile(Error **errp)
 {
     g_autoptr(GString) buf = g_string_new("");
diff --git a/accel/tcg/tb-stats.c b/accel/tcg/tb-stats.c
index 139f049ffc..4b358cb421 100644
--- a/accel/tcg/tb-stats.c
+++ b/accel/tcg/tb-stats.c
@@ -11,14 +11,18 @@ 
 #include "disas/disas.h"
 #include "exec/exec-all.h"
 #include "tcg/tcg.h"
+#include "qapi/error.h"
 
 #include "qemu/qemu-print.h"
 #include "qemu/timer.h"
+#include "qemu/log.h"
 
 #include "exec/tb-stats.h"
 #include "exec/tb-flush.h"
 #include "tb-context.h"
 
+#include "internal.h"
+
 /* TBStatistic collection controls */
 enum TBStatsStatus {
     TB_STATS_DISABLED = 0,
@@ -31,8 +35,23 @@  static uint32_t default_tbstats_flag;
 /* only accessed in safe work */
 static GList *last_search;
 
+static int id = 1; /* display_id increment counter */
 uint64_t dev_time;
 
+static TBStatistics *get_tbstats_by_id(int id)
+{
+    GList *iter;
+
+    for (iter = last_search; iter; iter = g_list_next(iter)) {
+        TBStatistics *tbs = iter->data;
+        if (tbs && tbs->display_id == id) {
+            return tbs;
+            break;
+        }
+    }
+    return NULL;
+}
+
 struct jit_profile_info {
     uint64_t translations;
     uint64_t aborted;
@@ -294,6 +313,309 @@  void init_tb_stats_htable(void)
     }
 }
 
+static void collect_tb_stats(void *p, uint32_t hash, void *userp)
+{
+    last_search = g_list_prepend(last_search, p);
+}
+
+static void count_invalid_tbs(gpointer data, gpointer user_data)
+{
+    TranslationBlock *tb = (TranslationBlock *) data;
+    unsigned *counter = (unsigned *) user_data;
+    if (tb->cflags & CF_INVALID) {
+        *counter = *counter + 1;
+    }
+}
+
+static int dump_tb_header(TBStatistics *tbs)
+{
+    unsigned g = stat_per_translation(tbs, code.num_guest_inst);
+    unsigned ops = stat_per_translation(tbs, code.num_tcg_ops);
+    unsigned ops_opt = stat_per_translation(tbs, code.num_tcg_ops_opt);
+    unsigned spills = stat_per_translation(tbs, code.spills);
+    unsigned h = stat_per_translation(tbs, code.out_len);
+    unsigned act = tbs->tbs->len;
+    unsigned invalid = 0;
+
+    float guest_host_prop = g ? ((float) h / g) : 0;
+
+    g_ptr_array_foreach(tbs->tbs, &count_invalid_tbs, &invalid);
+
+    qemu_log("TB id:%d | phys:0x"TB_PAGE_ADDR_FMT" virt:0x"TARGET_FMT_lx
+             " flags:0x%08x %d inv/%d\n",
+             tbs->display_id, tbs->phys_pc, tbs->pc, tbs->flags,
+             invalid, act);
+
+    if (tbs_stats_enabled(tbs, TB_EXEC_STATS)) {
+        qemu_log("\t| exec:%lu/%lu guest inst cov:%.2f%%\n",
+                tbs->executions.normal,
+                tbs->executions.atomic, tbs->executions.coverage / 100.0f);
+    }
+
+    if (tbs_stats_enabled(tbs, TB_JIT_STATS)) {
+        qemu_log("\t| trans:%lu ints: g:%u op:%u op_opt:%u spills:%d"
+             "\n\t| h/g (host bytes / guest insts): %f\n",
+             tbs->translations.total, g, ops, ops_opt, spills, guest_host_prop);
+    }
+
+    if (tbs_stats_enabled(tbs, TB_JIT_TIME)) {
+        qemu_log("\t| time to gen at 2.4GHz => code:%0.2lf(ns) IR:%0.2lf(ns)\n",
+             tbs->gen_times.code / 2.4, tbs->gen_times.ir / 2.4);
+    }
+
+    qemu_log("\n");
+
+    return act - invalid;
+}
+
+static gint
+inverse_sort_tbs(gconstpointer p1, gconstpointer p2, gpointer psort_by)
+{
+    const TBStatistics *tbs1 = (TBStatistics *) p1;
+    const TBStatistics *tbs2 = (TBStatistics *) p2;
+    int sort_by = *((enum SortBy *) psort_by);
+    unsigned long c1 = 0;
+    unsigned long c2 = 0;
+
+    if (sort_by == SORT_BY_SPILLS) {
+        c1 = stat_per_translation(tbs1, code.spills);
+        c2 = stat_per_translation(tbs2, code.spills);
+    } else if (sort_by == SORT_BY_HOTNESS) {
+        c1 = stat_per_translation(tbs1, executions.normal);
+        c2 = stat_per_translation(tbs2, executions.normal);
+    } else if (sort_by == SORT_BY_HG) {
+        if (tbs1->code.num_guest_inst == 0) {
+            return -1;
+        }
+        if (tbs2->code.num_guest_inst == 0) {
+            return 1;
+        }
+
+        c1 = tbs1->code.out_len / tbs1->code.num_guest_inst;
+        c2 = tbs2->code.out_len / tbs2->code.num_guest_inst;
+    }
+    return c1 < c2 ? 1 : c1 == c2 ? 0 : -1;
+}
+
+static void dump_last_search_headers(int count)
+{
+    if (!last_search) {
+        qemu_log("No data collected yet\n");
+        return;
+    }
+
+    GList *l = last_search;
+    while (l != NULL && count--) {
+        TBStatistics *tbs = (TBStatistics *) l->data;
+        GList *next = l->next;
+        dump_tb_header(tbs);
+        l = next;
+    }
+}
+
+static uint64_t calculate_last_search_coverages(void)
+{
+    uint64_t total_exec_count = 0;
+    GList *i;
+
+    /* Compute total execution count for all tbs */
+    for (i = last_search; i; i = i->next) {
+        TBStatistics *tbs = (TBStatistics *) i->data;
+        total_exec_count +=
+            (tbs->executions.atomic + tbs->executions.normal)
+                * tbs->code.num_guest_inst;
+    }
+
+    for (i = last_search; i; i = i->next) {
+        TBStatistics *tbs = (TBStatistics *) i->data;
+        uint64_t tb_total_execs =
+            (tbs->executions.atomic + tbs->executions.normal)
+                * tbs->code.num_guest_inst;
+        tbs->executions.coverage =
+            (10000 * tb_total_execs) / (total_exec_count + 1);
+    }
+
+    return total_exec_count;
+}
+
+static void do_dump_tbs_info(int total, int sort_by)
+{
+    id = 1;
+    GList *i;
+    int count = total;
+
+    g_list_free(last_search);
+    last_search = NULL;
+
+    qht_iter(&tb_ctx.tb_stats, collect_tb_stats, NULL);
+
+    last_search = g_list_sort_with_data(last_search, inverse_sort_tbs,
+                                        &sort_by);
+
+    if (!last_search) {
+        qemu_printf("No data collected yet!\n");
+        return;
+    }
+
+    calculate_last_search_coverages();
+
+    for (i = last_search; i && count--; i = i->next) {
+        TBStatistics *tbs = (TBStatistics *) i->data;
+        tbs->display_id = id++;
+    }
+
+    /* free the unused bits */
+    if (i) {
+        if (i->next) {
+            i->next->prev = NULL;
+        }
+        g_list_free(i->next);
+        i->next = NULL;
+    }
+
+    dump_last_search_headers(total);
+}
+
+struct tbs_dump_info {
+    int count;
+    int sort_by;
+};
+
+static void do_dump_tbs_info_safe(CPUState *cpu, run_on_cpu_data tbdi)
+{
+    struct tbs_dump_info *info = tbdi.host_ptr;
+    qemu_log_to_monitor(true);
+    do_dump_tbs_info(info->count, info->sort_by);
+    qemu_log_to_monitor(false);
+    g_free(info);
+}
+
+/*
+ * When we dump_tbs_info on a live system via the HMP we want to
+ * ensure the system is quiessent before we start outputting stuff.
+ * Otherwise we could pollute the output with other logging output.
+ */
+
+void dump_tbs_info(int count, int sort_by, bool use_monitor)
+{
+    if (use_monitor) {
+        struct tbs_dump_info *tbdi = g_new(struct tbs_dump_info, 1);
+        tbdi->count = count;
+        tbdi->sort_by = sort_by;
+        async_safe_run_on_cpu(first_cpu, do_dump_tbs_info_safe,
+                              RUN_ON_CPU_HOST_PTR(tbdi));
+    } else {
+        do_dump_tbs_info(count, sort_by);
+    }
+}
+
+/*
+ * We cannot always re-generate the code even if we know there are
+ * valid translations still in the cache. The reason being the guest
+ * may have un-mapped the page code. In real life this would be
+ * un-reachable as the jump cache is cleared and the following QHT
+ * lookup will do a get_page_addr_code() and fault.
+ *
+ * TODO: can we do this safely? We need to
+ *  a) somehow recover the mmu_idx for this translation
+ *  b) probe MMU_INST_FETCH to know it will succeed
+ */
+static GString *get_code_string(TBStatistics *tbs, int log_flags)
+{
+    int old_log_flags = qemu_loglevel;
+
+    CPUState *cpu = first_cpu;
+    uint32_t cflags = curr_cflags(cpu);
+    TranslationBlock *tb = NULL;
+
+    GString *code_s = g_string_new(NULL);
+    qemu_log_to_string(true, code_s);
+
+    Error *err = NULL;
+    if (!qemu_set_log(log_flags, &err)) {
+        g_string_append_printf(code_s, "%s", error_get_pretty(err));
+        error_free(err);
+    }
+
+    if (sigsetjmp(cpu->jmp_env, 0) == 0) {
+        mmap_lock();
+        tb = tb_gen_code(cpu, tbs->pc, tbs->cs_base, tbs->flags, cflags);
+        tb_phys_invalidate(tb, -1);
+        mmap_unlock();
+    } else {
+        /*
+         * The mmap_lock is dropped by tb_gen_code if it runs out of
+         * memory.
+         */
+        qemu_log("\ncould not gen code for this TB (no longer mapped?)\n");
+        assert_no_pages_locked();
+    }
+
+    qemu_set_log(old_log_flags, &err);
+    qemu_log_to_string(false, NULL);
+
+    return code_s;
+}
+
+static void do_tb_dump_with_statistics(TBStatistics *tbs, int log_flags)
+{
+    g_autoptr(GString) code_s = NULL;
+
+    qemu_log("\n------------------------------\n\n");
+
+    if (dump_tb_header(tbs) > 0) {
+        code_s = get_code_string(tbs, log_flags);
+    } else {
+        code_s = g_string_new("cannot re-translate non-active translation");
+    }
+    qemu_log("%s", code_s->str);
+    qemu_log("------------------------------\n");
+}
+
+struct tb_dump_info {
+    int id;
+    int log_flags;
+    bool use_monitor;
+};
+
+static void do_dump_tb_info_safe(CPUState *cpu, run_on_cpu_data info)
+{
+    struct tb_dump_info *tbdi = (struct tb_dump_info *) info.host_ptr;
+
+    if (!last_search) {
+        qemu_log("no search on record\n");
+        return;
+    }
+
+    qemu_log_to_monitor(tbdi->use_monitor);
+
+    TBStatistics *tbs = get_tbstats_by_id(tbdi->id);
+    if (tbs) {
+        do_tb_dump_with_statistics(tbs, tbdi->log_flags);
+    } else {
+        qemu_log("no TB statitics found with id %d\n", tbdi->id);
+    }
+
+    qemu_log_to_monitor(false);
+
+    g_free(tbdi);
+}
+
+void dump_tb_info(int id, int log_mask, bool use_monitor)
+{
+    struct tb_dump_info *tbdi = g_new(struct tb_dump_info, 1);
+
+    tbdi->id = id;
+    tbdi->log_flags = log_mask;
+    tbdi->use_monitor = use_monitor;
+
+    async_safe_run_on_cpu(first_cpu, do_dump_tb_info_safe,
+                          RUN_ON_CPU_HOST_PTR(tbdi));
+
+    /* tbdi free'd by do_dump_tb_info_safe */
+}
+
+
 void enable_collect_tb_stats(void)
 {
     tcg_collect_tb_stats = TB_STATS_RUNNING;
diff --git a/disas/disas.c b/disas/disas.c
index 0d2d06c2ec..0f31733646 100644
--- a/disas/disas.c
+++ b/disas/disas.c
@@ -8,6 +8,8 @@ 
 #include "hw/core/cpu.h"
 #include "exec/memory.h"
 
+#include "qemu/log-for-trace.h"
+
 /* Filled in by elfload.c.  Simplistic, but will do for now. */
 struct syminfo *syminfos = NULL;
 
@@ -199,6 +201,24 @@  static void initialize_debug_host(CPUDebug *s)
 #endif
 }
 
+static int
+__attribute__((format(printf, 2, 3)))
+fprintf_log(FILE *a, const char *b, ...)
+{
+    va_list ap;
+    va_start(ap, b);
+
+    if (!to_string) {
+        vfprintf(a, b, ap);
+    } else {
+        qemu_vlog(b, ap);
+    }
+
+    va_end(ap);
+
+    return 1;
+}
+
 /* Disassemble this for me please... (debugging).  */
 void target_disas(FILE *out, CPUState *cpu, uint64_t code, size_t size)
 {
@@ -207,7 +227,7 @@  void target_disas(FILE *out, CPUState *cpu, uint64_t code, size_t size)
     CPUDebug s;
 
     disas_initialize_debug_target(&s, cpu);
-    s.info.fprintf_func = fprintf;
+    s.info.fprintf_func = fprintf_log;
     s.info.stream = out;
     s.info.buffer_vma = code;
     s.info.buffer_length = size;
@@ -221,9 +241,9 @@  void target_disas(FILE *out, CPUState *cpu, uint64_t code, size_t size)
     }
 
     for (pc = code; size > 0; pc += count, size -= count) {
-        fprintf(out, "0x%08" PRIx64 ":  ", pc);
+        fprintf_log(out, "0x%08" PRIx64 ":  ", pc);
         count = s.info.print_insn(pc, &s.info);
-        fprintf(out, "\n");
+        fprintf_log(out, "\n");
         if (count < 0) {
             break;
         }
diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
index 47d63d26db..01d9658aea 100644
--- a/hmp-commands-info.hx
+++ b/hmp-commands-info.hx
@@ -262,6 +262,22 @@  ERST
         .params     = "",
         .help       = "show dynamic compiler info",
     },
+    {
+        .name       = "tb-list",
+        .args_type  = "number:i?,sortedby:s?",
+        .params     = "[number sortedby]",
+        .help       = "show a [number] translated blocks sorted by [sortedby]"
+                      "sortedby opts: hotness hg spills",
+        .cmd        = hmp_info_tblist,
+    },
+    {
+        .name       = "tb",
+        .args_type  = "id:i,flags:s?",
+        .params     = "id [flag1,flag2,...]",
+        .help       = "show information about one translated block by id."
+                      "dump flags can be used to set dump code level: out_asm in_asm op",
+        .cmd        = hmp_info_tb,
+    },
 #endif
 
 SRST
diff --git a/include/exec/tb-stats.h b/include/exec/tb-stats.h
index 30b788f7b2..f2a6b09da9 100644
--- a/include/exec/tb-stats.h
+++ b/include/exec/tb-stats.h
@@ -36,8 +36,11 @@ 
 enum SortBy { SORT_BY_HOTNESS, SORT_BY_HG /* Host/Guest */, SORT_BY_SPILLS };
 enum TbstatsCmd { START, PAUSE, STOP, FILTER };
 
+#define tbs_stats_enabled(tbs, JIT_STATS) \
+    (tbs && (tbs->stats_enabled & JIT_STATS))
+
 #define tb_stats_enabled(tb, JIT_STATS) \
-    (tb && tb->tb_stats && (tb->tb_stats->stats_enabled & JIT_STATS))
+    (tb && tb->tb_stats && tbs_stats_enabled(tb->tb_stats, JIT_STATS))
 
 #define stat_per_translation(stat, name) \
     (stat->translations.total ? stat->name / stat->translations.total : 0)
@@ -66,6 +69,8 @@  struct TBStatistics {
     struct {
         unsigned long normal;
         unsigned long atomic;
+        /* filled only when dumping x% cover set */
+        uint16_t coverage;
     } executions;
 
     /* JIT Stats - protected by lock */
@@ -88,7 +93,6 @@  struct TBStatistics {
 
     struct {
         unsigned long total;
-        unsigned long uncached;
         unsigned long spanning;
     } translations;
 
@@ -108,6 +112,9 @@  struct TBStatistics {
         uint64_t la;
         uint64_t code;
     } gen_times;
+
+    /* HMP information - used for referring to previous search */
+    int display_id;
 };
 
 bool tb_stats_cmp(const void *ap, const void *bp);
@@ -132,4 +139,26 @@  void do_hmp_tbstats_safe(CPUState *cpu, run_on_cpu_data icmd);
  */
 void tbstats_reset_tbs(void);
 
+/**
+ * dump_tbs_info: report the hottest blocks
+ *
+ * @count: the limit of hotblocks
+ * @sort_by: property in which the dump will be sorted
+ * @use_monitor: redirect output to monitor
+ *
+ * Report the hottest blocks to either the log or monitor
+ */
+void dump_tbs_info(int count, int sort_by, bool use_monitor);
+
+/**
+ * dump_tb_info: dump information about one TB
+ *
+ * @id: the display id of the block (from previous search)
+ * @mask: the temporary logging mask
+ * @Use_monitor: redirect output to monitor
+ *
+ * Re-run a translation of a block at addr for the purposes of debug output
+ */
+void dump_tb_info(int id, int log_mask, bool use_monitor);
+
 #endif
diff --git a/include/monitor/hmp.h b/include/monitor/hmp.h
index 2e7f141754..acdd6f1561 100644
--- a/include/monitor/hmp.h
+++ b/include/monitor/hmp.h
@@ -182,5 +182,7 @@  void hmp_boot_set(Monitor *mon, const QDict *qdict);
 void hmp_info_mtree(Monitor *mon, const QDict *qdict);
 void hmp_info_cryptodev(Monitor *mon, const QDict *qdict);
 void hmp_tbstats(Monitor *mon, const QDict *qdict);
+void hmp_info_tblist(Monitor *mon, const QDict *qdict);
+void hmp_info_tb(Monitor *mon, const QDict *qdict);
 
 #endif
diff --git a/include/qemu/log-for-trace.h b/include/qemu/log-for-trace.h
index d47c9cd446..5d0afc56c7 100644
--- a/include/qemu/log-for-trace.h
+++ b/include/qemu/log-for-trace.h
@@ -20,6 +20,9 @@ 
 
 /* Private global variable, don't use */
 extern int qemu_loglevel;
+extern bool to_string;
+
+extern int32_t max_num_hot_tbs_to_dump;
 
 #define LOG_TRACE          (1 << 15)
 
@@ -30,6 +33,7 @@  static inline bool qemu_loglevel_mask(int mask)
 }
 
 /* main logging function */
-void G_GNUC_PRINTF(1, 2) qemu_log(const char *fmt, ...);
+int G_GNUC_PRINTF(1, 2) qemu_log(const char *fmt, ...);
+int G_GNUC_PRINTF(1, 0) qemu_vlog(const char *fmt, va_list va);
 
 #endif
diff --git a/include/qemu/log.h b/include/qemu/log.h
index 6f3b8091cd..26b33151f3 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -85,6 +85,8 @@  extern const QEMULogItem qemu_log_items[];
 bool qemu_set_log(int log_flags, Error **errp);
 bool qemu_set_log_filename(const char *filename, Error **errp);
 bool qemu_set_log_filename_flags(const char *name, int flags, Error **errp);
+void qemu_log_to_monitor(bool enable);
+void qemu_log_to_string(bool enable, GString *s);
 void qemu_set_dfilter_ranges(const char *ranges, Error **errp);
 bool qemu_log_in_addr_range(uint64_t addr);
 int qemu_str_to_log_mask(const char *str);
diff --git a/util/log.c b/util/log.c
index 7ae471d97c..6477eb5a5f 100644
--- a/util/log.c
+++ b/util/log.c
@@ -50,6 +50,8 @@  int qemu_loglevel;
 static bool log_per_thread;
 static GArray *debug_regions;
 int32_t max_num_hot_tbs_to_dump;
+static bool to_monitor;
+bool to_string;
 
 /* Returns true if qemu_log() will really write somewhere. */
 bool qemu_log_enabled(void)
@@ -146,19 +148,6 @@  void qemu_log_unlock(FILE *logfile)
     }
 }
 
-void qemu_log(const char *fmt, ...)
-{
-    FILE *f = qemu_log_trylock();
-    if (f) {
-        va_list ap;
-
-        va_start(ap, fmt);
-        vfprintf(f, fmt, ap);
-        va_end(ap);
-        qemu_log_unlock(f);
-    }
-}
-
 static void __attribute__((__constructor__)) startup(void)
 {
     qemu_mutex_init(&global_mutex);
@@ -206,6 +195,55 @@  valid_filename_template(const char *filename, bool per_thread, Error **errp)
     return filename ? vft_strdup : vft_stderr;
 }
 
+GString *string;
+
+int qemu_vlog(const char *fmt, va_list va)
+{
+    int ret = 0;
+
+    if (to_string && string) {
+        g_string_append_vprintf(string, fmt, va);
+    } else if (to_monitor) {
+        ret = qemu_vprintf(fmt, va);
+    } else {
+        FILE *f = qemu_log_trylock();
+        if (f) {
+            ret = vfprintf(f, fmt, va);
+        }
+        qemu_log_unlock(f);
+    }
+
+    /* Don't pass back error results.  */
+    if (ret < 0) {
+        ret = 0;
+    }
+    return ret;
+}
+
+/* Return the number of characters emitted.  */
+int qemu_log(const char *fmt, ...)
+{
+    int ret = 0;
+    va_list ap;
+
+    va_start(ap, fmt);
+    ret = qemu_vlog(fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
+void qemu_log_to_monitor(bool enable)
+{
+    to_monitor = enable;
+}
+
+void qemu_log_to_string(bool enable, GString *s)
+{
+    to_string = enable;
+    string = s;
+}
+
 /* enable or disable low levels log */
 static bool qemu_set_log_internal(const char *filename, bool changed_name,
                                   int log_flags, Error **errp)
@@ -523,6 +561,7 @@  int qemu_str_to_log_mask(const char *str)
             trace_enable_events((*tmp) + 6);
             mask |= LOG_TRACE;
 #endif
+#ifdef CONFIG_TCG
         } else if (g_str_has_prefix(*tmp, "tb_stats")) {
             mask |= CPU_LOG_TB_STATS;
             set_default_tbstats_flag(TB_ALL_STATS);
@@ -553,6 +592,7 @@  int qemu_str_to_log_mask(const char *str)
                 }
                 set_default_tbstats_flag(flags);
             }
+#endif
         } else {
             for (item = qemu_log_items; item->mask != 0; item++) {
                 if (g_str_equal(*tmp, item->name)) {