| Message ID | o2hfdaac4d51004151803j9d1069d2nd9dfe3297bb64439@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
Jun Koi schrieb: > (Thanks to Jan for comments on the last patch) > > Qemu has a command named singlestep, which reduces the translated code > block to be only one instruction. > However, there is one flaw when this command is triggered via monitor > interface: we do not flush all the current TBs, so we will miss > single-step on already translated code. > This patch fixes the problem by flushing all the TB to force new code > generation. > > Signed-off-by: Jun Koi <junkoi2004@gmail.com> > > > > diff --git a/monitor.c b/monitor.c > index 5659991..948b861 100644 > --- a/monitor.c > +++ b/monitor.c > @@ -1190,8 +1190,14 @@ static void do_log(Monitor *mon, const QDict > *qdict) > static void do_singlestep(Monitor *mon, const QDict *qdict) > { > const char *option = qdict_get_try_str(qdict, "option"); > + CPUState *env; > + > if (!option || !strcmp(option, "on")) { > singlestep = 1; > + /* flush all the TBs to force new code generation */ > + for (env = first_cpu; env != NULL; env = env->next_cpu) { > + tb_flush(env); > + } > } else if (!strcmp(option, "off")) { > singlestep = 0; > } else { Hi, sorry that my feedback comes rather late. I read the discussion, but had no time to answer. I wrote the code for the singlestep command line and monitor option (which already existed before as a compile time option) and still use it frequently. Up to now, I did not miss the tb flushing, but I see that it might be useful in certain cases. My typical use cases for "singlestep" are * Compare execution of same code (usually a user mode program or a kernel) running in different environments (32 bit or 64 bit host, big or little endian host, different host architectures). In combination with -D in_asm,cpu it is possible to find wrong tcg code by comparing the resulting qemu.log files. * Use singlestep to slow down the execution (yes, this is sometimes useful). In most cases, I use the command line option, but sometimes I use the monitor command, too. There is no logical relation between switching singlestep on or off and tb flushing. If there is the need for tb flush, I'd suggest to add a new monitor command. If the translated tbs should match the singlestep setting, you would also have to flush them when singlestep is disabled: in that case, the translated tbs only contain a single target instruction, so they are not very efficient - and they remain so even after singlestep was disabled. So either flush for singlestep on and off, or better add a new monitor command which flushes tbs. Regards, Stefan
diff --git a/monitor.c b/monitor.c index 5659991..948b861 100644 --- a/monitor.c +++ b/monitor.c @@ -1190,8 +1190,14 @@ static void do_log(Monitor *mon, const QDict *qdict) static void do_singlestep(Monitor *mon, const QDict *qdict) { const char *option = qdict_get_try_str(qdict, "option"); + CPUState *env; + if (!option || !strcmp(option, "on")) { singlestep = 1; + /* flush all the TBs to force new code generation */ + for (env = first_cpu; env != NULL; env = env->next_cpu) { + tb_flush(env); + } } else if (!strcmp(option, "off")) { singlestep = 0; } else {
(Thanks to Jan for comments on the last patch) Qemu has a command named singlestep, which reduces the translated code block to be only one instruction. However, there is one flaw when this command is triggered via monitor interface: we do not flush all the current TBs, so we will miss single-step on already translated code. This patch fixes the problem by flushing all the TB to force new code generation. Signed-off-by: Jun Koi <junkoi2004@gmail.com>