This commit adds 'one-insn-per-tb' as a property on the TCG accelerator object, so you can enable it with -accel tcg,one-insn-per-tb=on It has the same behaviour as the existing '-singlestep' command line option. We use a different name because 'singlestep' has always been a confusing choice, because it doesn't have anything to do with single-stepping the CPU. What it does do is force TCG emulation to put one guest instruction in each TB, which can be useful in some situations (such as analysing debug logs). The existing '-singlestep' commandline options are decoupled from the global 'singlestep' variable and instead now are syntactic sugar for setting the accel property. (These can then go away after a deprecation period.) The global variable remains for the moment as: * what the TCG code looks at to change its behaviour * what HMP and QMP use to query and set the behaviour In the following commits we'll clean those up to not directly look at the global variable. Signed-off-by: Peter Maydell <peter.maydell(a)linaro.org&gt; Reviewed-by: Richard Henderson <richard.henderson(a)linaro.org&gt; --- accel/tcg/tcg-all.c | 21 +++++++++++++++++++++ bsd-user/main.c | 8 ++++++-- linux-user/main.c | 8 ++++++-- softmmu/vl.c | 17 +++++++++++++++-- qemu-options.hx | 7 +++++++ 5 files changed, 55 insertions(+), 6 deletions(-) diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c index 5dab1ae9dd3..fcf361c8db6 100644 --- a/accel/tcg/tcg-all.c +++ b/accel/tcg/tcg-all.c @@ -42,6 +42,7 @@ struct TCGState { AccelState parent_obj; bool mttcg_enabled; + bool one_insn_per_tb; int splitwx_enabled; unsigned long tb_size; }; @@ -208,6 +209,20 @@ static void tcg_set_splitwx(Object *obj, bool value, Error **errp) s->splitwx_enabled = value; } +static bool tcg_get_one_insn_per_tb(Object *obj, Error **errp) +{ + TCGState *s = TCG_STATE(obj); + return s->one_insn_per_tb; +} + +static void tcg_set_one_insn_per_tb(Object *obj, bool value, Error **errp) +{ + TCGState *s = TCG_STATE(obj); + s->one_insn_per_tb = value; + /* For the moment, set the global also: this changes the behaviour */ + singlestep = value; +} + static int tcg_gdbstub_supported_sstep_flags(void) { /* @@ -245,6 +260,12 @@ static void tcg_accel_class_init(ObjectClass *oc, void *data) tcg_get_splitwx, tcg_set_splitwx); object_class_property_set_description(oc, "split-wx", "Map jit pages into separate RW and RX regions"); + + object_class_property_add_bool(oc, "one-insn-per-tb", + tcg_get_one_insn_per_tb, + tcg_set_one_insn_per_tb); + object_class_property_set_description(oc, "one-insn-per-tb", + "Only put one guest insn in each translation block"); } static const TypeInfo tcg_accel_type = { diff --git a/bsd-user/main.c b/bsd-user/main.c index babc3b009b6..09b84da190c 100644 --- a/bsd-user/main.c +++ b/bsd-user/main.c @@ -50,6 +50,7 @@ #include "target_arch_cpu.h" int singlestep; +static bool opt_one_insn_per_tb; uintptr_t guest_base; bool have_guest_base; /* @@ -386,7 +387,7 @@ int main(int argc, char **argv) } else if (!strcmp(r, "seed")) { seed_optarg = optarg; } else if (!strcmp(r, "singlestep")) { - singlestep = 1; + opt_one_insn_per_tb = true; } else if (!strcmp(r, "strace")) { do_strace = 1; } else if (!strcmp(r, "trace")) { @@ -444,9 +445,12 @@ int main(int argc, char **argv) /* init tcg before creating CPUs and to get qemu_host_page_size */ { - AccelClass *ac = ACCEL_GET_CLASS(current_accel()); + AccelState *accel = current_accel(); + AccelClass *ac = ACCEL_GET_CLASS(accel); accel_init_interfaces(ac); + object_property_set_bool(OBJECT(accel), "one-insn-per-tb", + opt_one_insn_per_tb, &error_abort); ac->init_machine(NULL); } cpu = cpu_create(cpu_type); diff --git a/linux-user/main.c b/linux-user/main.c index fe03293516a..489694ad654 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -69,6 +69,7 @@ char *exec_path; char real_exec_path[PATH_MAX]; int singlestep; +static bool opt_one_insn_per_tb; static const char *argv0; static const char *gdbstub; static envlist_t *envlist; @@ -411,7 +412,7 @@ static void handle_arg_reserved_va(const char *arg) static void handle_arg_singlestep(const char *arg) { - singlestep = 1; + opt_one_insn_per_tb = true; } static void handle_arg_strace(const char *arg) @@ -777,9 +778,12 @@ int main(int argc, char **argv, char **envp) /* init tcg before creating CPUs and to get qemu_host_page_size */ { - AccelClass *ac = ACCEL_GET_CLASS(current_accel()); + AccelState *accel = current_accel(); + AccelClass *ac = ACCEL_GET_CLASS(accel); accel_init_interfaces(ac); + object_property_set_bool(OBJECT(accel), "one-insn-per-tb", + opt_one_insn_per_tb, &error_abort); ac->init_machine(NULL); } cpu = cpu_create(cpu_type); diff --git a/softmmu/vl.c b/softmmu/vl.c index ea20b23e4c8..492b5fe65e6 100644 --- a/softmmu/vl.c +++ b/softmmu/vl.c @@ -182,6 +182,7 @@ static const char *log_file; static bool list_data_dirs; static const char *qtest_chrdev; static const char *qtest_log; +static bool opt_one_insn_per_tb; static int has_defaults = 1; static int default_serial = 1; @@ -2220,7 +2221,19 @@ static int do_configure_accelerator(void *opaque, QemuOpts *opts, Error **errp) qemu_opt_foreach(opts, accelerator_set_property, accel, &error_fatal); - + /* + * If legacy -singlestep option is set, honour it for TCG and + * silently ignore for any other accelerator (which is how this + * option has always behaved). + */ + if (opt_one_insn_per_tb) { + /* + * This will always succeed for TCG, and we want to ignore + * the error from trying to set a nonexistent property + * on any other accelerator. + */ + object_property_set_bool(OBJECT(accel), "one-insn-per-tb", true, NULL); + } ret = accel_init_machine(accel, current_machine); if (ret < 0) { if (!qtest_with_kvm || ret != -ENOENT) { @@ -2955,7 +2968,7 @@ void qemu_init(int argc, char **argv) qdict_put_str(machine_opts_dict, "firmware", optarg); break; case QEMU_OPTION_singlestep: - singlestep = 1; + opt_one_insn_per_tb = true; break; case QEMU_OPTION_S: autostart = 0; diff --git a/qemu-options.hx b/qemu-options.hx index 59bdf67a2c5..1dffd36884e 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -182,6 +182,7 @@ DEF("accel", HAS_ARG, QEMU_OPTION_accel, " igd-passthru=on|off (enable Xen integrated Intel graphics passthrough, default=off)\n" " kernel-irqchip=on|off|split controls accelerated irqchip support (default=on)\n" " kvm-shadow-mem=size of KVM shadow MMU in bytes\n" + " one-insn-per-tb=on|off (one guest instruction per TCG translation block)\n" " split-wx=on|off (enable TCG split w^x mapping)\n" " tb-size=n (TCG translation block cache size)\n" " dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n" @@ -210,6 +211,12 @@ SRST ``kvm-shadow-mem=size`` Defines the size of the KVM shadow MMU. + ``one-insn-per-tb=on|off`` + Makes the TCG accelerator put only one guest instruction into + each translation block. This slows down emulation a lot, but + can be useful in some situations, such as when trying to analyse + the logs produced by the ``-d`` option. + ``split-wx=on|off`` Controls the use of split w^x mapping for the TCG code generation buffer. Some operating systems require this to be enabled, and in -- 2.34.1

On Tue, 18 Apr 2023 at 09:05, Richard Henderson <richard.henderson(a)linaro.org&gt; wrote: True at the moment, but if we do ever want to do that refactoring to use a tcg_global_cflags, then we will need the TCGState field, because you can't go from a tcg_global_cflags value back to "what are the one_insn_per_tb and nochain settings currently?". thanks -- PMM

The '-singlestep' option is confusing, because it doesn't actually have anything to do with single-stepping the CPU. What it does do is force TCG emulation to put one guest instruction in each TB, which can be useful in some situations. Create a new command line argument -one-insn-per-tb, so we can document that -singlestep is just a deprecated synonym for it, and eventually perhaps drop it. Signed-off-by: Peter Maydell <peter.maydell(a)linaro.org&gt; Reviewed-by: Richard Henderson <richard.henderson(a)linaro.org&gt; Reviewed-by: Warner Losh <imp(a)bsdimp.com&gt; --- docs/user/main.rst | 7 ++++++- linux-user/main.c | 9 ++++++--- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/docs/user/main.rst b/docs/user/main.rst index 6f2ffa080f7..f9ac701f4b1 100644 --- a/docs/user/main.rst +++ b/docs/user/main.rst @@ -93,8 +93,13 @@ Debug options: ``-g port`` Wait gdb connection to port +``-one-insn-per-tb`` + Run the emulation with one guest instruction per translation block. + This slows down emulation a lot, but can be useful in some situations, + such as when trying to analyse the logs produced by the ``-d`` option. + ``-singlestep`` - Run the emulation in single step mode. + This is a deprecated synonym for the ``-one-insn-per-tb`` option. Environment variables: diff --git a/linux-user/main.c b/linux-user/main.c index c7020b413bc..5defe5a6db8 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -409,7 +409,7 @@ static void handle_arg_reserved_va(const char *arg) reserved_va = val ? val - 1 : 0; } -static void handle_arg_singlestep(const char *arg) +static void handle_arg_one_insn_per_tb(const char *arg) { opt_one_insn_per_tb = true; } @@ -500,8 +500,11 @@ static const struct qemu_argument arg_table[] = { "logfile", "write logs to 'logfile' (default stderr)"}, {"p", "QEMU_PAGESIZE", true, handle_arg_pagesize, "pagesize", "set the host page size to 'pagesize'"}, - {"singlestep", "QEMU_SINGLESTEP", false, handle_arg_singlestep, - "", "run in singlestep mode"}, + {"one-insn-per-tb", + "QEMU_ONE_INSN_PER_TB", false, handle_arg_one_insn_per_tb, + "", "run with one guest instruction per emulated TB"}, + {"singlestep", "QEMU_SINGLESTEP", false, handle_arg_one_insn_per_tb, + "", "deprecated synonym for -one-insn-per-tb"}, {"strace", "QEMU_STRACE", false, handle_arg_strace, "", "log system calls"}, {"seed", "QEMU_RAND_SEED", true, handle_arg_seed, -- 2.34.1

On Thu, 20 Apr 2023 at 10:13, Philippe Mathieu-Daudé <philmd(a)linaro.org&gt; wrote: There's not a lot of space in the -help output, and I think in context it's clear enough without. thanks -- PMM

The '-singlestep' option is confusing, because it doesn't actually have anything to do with single-stepping the CPU. What it does do is force TCG emulation to put one guest instruction in each TB, which can be useful in some situations. Create a new command line argument -one-insn-per-tb, so we can document that -singlestep is just a deprecated synonym for it, and eventually perhaps drop it. Signed-off-by: Peter Maydell <peter.maydell(a)linaro.org&gt; Reviewed-by: Warner Losh <imp(a)bsdimp.com&gt; Reviewed-by: Richard Henderson <richard.henderson(a)linaro.org&gt; --- docs/user/main.rst | 7 ++++++- bsd-user/main.c | 5 +++-- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/docs/user/main.rst b/docs/user/main.rst index f9ac701f4b1..f4786353965 100644 --- a/docs/user/main.rst +++ b/docs/user/main.rst @@ -247,5 +247,10 @@ Debug options: ``-p pagesize`` Act as if the host page size was 'pagesize' bytes +``-one-insn-per-tb`` + Run the emulation with one guest instruction per translation block. + This slows down emulation a lot, but can be useful in some situations, + such as when trying to analyse the logs produced by the ``-d`` option. + ``-singlestep`` - Run the emulation in single step mode. + This is a deprecated synonym for the ``-one-insn-per-tb`` option. diff --git a/bsd-user/main.c b/bsd-user/main.c index a9e5a127d38..cd8b2a670f7 100644 --- a/bsd-user/main.c +++ b/bsd-user/main.c @@ -162,7 +162,8 @@ static void usage(void) "-d item1[,...] enable logging of specified items\n" " (use '-d help' for a list of log items)\n" "-D logfile write logs to 'logfile' (default stderr)\n" - "-singlestep always run in singlestep mode\n" + "-one-insn-per-tb run with one guest instruction per emulated TB\n" + "-singlestep deprecated synonym for -one-insn-per-tb\n" "-strace log system calls\n" "-trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n" " specify tracing options\n" @@ -385,7 +386,7 @@ int main(int argc, char **argv) (void) envlist_unsetenv(envlist, "LD_PRELOAD"); } else if (!strcmp(r, "seed")) { seed_optarg = optarg; - } else if (!strcmp(r, "singlestep")) { + } else if (!strcmp(r, "singlestep") || !strcmp(r, "one-insn-per-tb")) { opt_one_insn_per_tb = true; } else if (!strcmp(r, "strace")) { do_strace = 1; -- 2.34.1

Document that the -singlestep command line option is now deprecated, as it is replaced by either the TCG accelerator property 'one-insn-per-tb' for system emulation or the new '-one-insn-per-tb' option for usermode emulation, and remove the only use of the deprecated syntax from a README. Signed-off-by: Peter Maydell <peter.maydell(a)linaro.org&gt; Reviewed-by: Richard Henderson <richard.henderson(a)linaro.org&gt; --- docs/about/deprecated.rst | 16 ++++++++++++++++ qemu-options.hx | 5 +++-- tcg/tci/README | 2 +- 3 files changed, 20 insertions(+), 3 deletions(-) diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 1ca9dc33d61..3c62671dac1 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -111,6 +111,22 @@ Use ``-machine acpi=off`` instead. The HAXM project has been retired (see https://github.com/intel/haxm#status). Use "whpx" (on Windows) or "hvf" (on macOS) instead. +``-singlestep`` (since 8.1) +''''''''''''''''''''''''''' + +The ``-singlestep`` option has been turned into an accelerator property, +and given a name that better reflects what it actually does. +Use ``-accel tcg,one-insn-per-tb=on`` instead. + +User-mode emulator command line arguments +----------------------------------------- + +``-singlestep`` (since 8.1) +''''''''''''''''''''''''''' + +The ``-singlestep`` option has been given a name that better reflects +what it actually does. For both linux-user and bsd-user, use the +new ``-one-insn-per-tb`` option instead. QEMU Machine Protocol (QMP) commands ------------------------------------ diff --git a/qemu-options.hx b/qemu-options.hx index 1dffd36884e..6a59e997497 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -4159,10 +4159,11 @@ SRST ERST DEF("singlestep", 0, QEMU_OPTION_singlestep, \ - "-singlestep always run in singlestep mode\n", QEMU_ARCH_ALL) + "-singlestep deprecated synonym for -accel tcg,one-insn-per-tb=on\n", QEMU_ARCH_ALL) SRST ``-singlestep`` - Run the emulation in single step mode. + This is a deprecated synonym for the TCG accelerator property + ``one-insn-per-tb``. ERST DEF("preconfig", 0, QEMU_OPTION_preconfig, \ diff --git a/tcg/tci/README b/tcg/tci/README index f72a40a395a..4a8b5b54018 100644 --- a/tcg/tci/README +++ b/tcg/tci/README @@ -49,7 +49,7 @@ The only difference from running QEMU with TCI to running without TCI should be speed. Especially during development of TCI, it was very useful to compare runs with and without TCI. Create /tmp/qemu.log by - qemu-system-i386 -d in_asm,op_opt,cpu -D /tmp/qemu.log -singlestep + qemu-system-i386 -d in_asm,op_opt,cpu -D /tmp/qemu.log -accel tcg,one-insn-per-tb=on once with interpreter and once without interpreter and compare the resulting qemu.log files. This is also useful to see the effects of additional -- 2.34.1

Currently we report whether the TCG accelerator is in 'one-insn-per-tb' mode in the 'info status' output. This is a pretty minor piece of TCG specific information, and we want to deprecate the 'singlestep' field of the associated QMP command. Move the 'one-insn-per-tb' reporting to 'info jit'. We don't need a deprecate-and-drop period for this because the HMP interface has no stability guarantees. Signed-off-by: Peter Maydell <peter.maydell(a)linaro.org&gt; --- The new 'accelerator settings' subsection of the output currently only has one item, but it would be a place to put other stuff, eg if we wanted to mention whether split-wx is enabled. --- accel/tcg/monitor.c | 14 ++++++++++++++ softmmu/runstate-hmp-cmds.c | 5 ++--- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/accel/tcg/monitor.c b/accel/tcg/monitor.c index 1450e160e95..92fce580f11 100644 --- a/accel/tcg/monitor.c +++ b/accel/tcg/monitor.c @@ -7,6 +7,7 @@ */ #include "qemu/osdep.h" +#include "qemu/accel.h" #include "qapi/error.h" #include "qapi/type-helpers.h" #include "qapi/qapi-commands-machine.h" @@ -36,6 +37,18 @@ static void dump_drift_info(GString *buf) } } +static void dump_accel_info(GString *buf) +{ + AccelState *accel = current_accel(); + bool one_insn_per_tb = object_property_get_bool(OBJECT(accel), + "one-insn-per-tb", + &error_fatal); + + g_string_append_printf(buf, "Accelerator settings:\n"); + g_string_append_printf(buf, "one-insn-per-tb: %s\n\n", + one_insn_per_tb ? "on" : "off"); +} + HumanReadableText *qmp_x_query_jit(Error **errp) { g_autoptr(GString) buf = g_string_new(""); @@ -45,6 +58,7 @@ HumanReadableText *qmp_x_query_jit(Error **errp) return NULL; } + dump_accel_info(buf); dump_exec_info(buf); dump_drift_info(buf); diff --git a/softmmu/runstate-hmp-cmds.c b/softmmu/runstate-hmp-cmds.c index 127521a483a..a477838dc5a 100644 --- a/softmmu/runstate-hmp-cmds.c +++ b/softmmu/runstate-hmp-cmds.c @@ -28,9 +28,8 @@ void hmp_info_status(Monitor *mon, const QDict *qdict) info = qmp_query_status(NULL); - monitor_printf(mon, "VM status: %s%s", - info->running ? "running" : "paused", - info->singlestep ? " (single step mode)" : ""); + monitor_printf(mon, "VM status: %s", + info->running ? "running" : "paused"); if (!info->running && info->status != RUN_STATE_PAUSED) { monitor_printf(mon, " (%s)", RunState_str(info->status)); -- 2.34.1

Markus -- could I trouble you for a quick review of this patch? It's the only one in the series that touches QMP. Everything else has been reviewed so otherwise this series is ready to go in. thanks -- PMM On Mon, 17 Apr 2023 at 17:40, Peter Maydell <peter.maydell(a)linaro.org&gt; wrote: