Re: [PATCH] tests/plugin: Remove duplicate insn log from libinsn.so

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> This is a perfectly natural occurrence for x86 "rep movb",
> where the "rep" prefix forms a counted loop of the one insn.
>
> During the tests/tcg/multiarch/memory test, this logging is
> triggered over 350000 times.  Within the context of cross-i386-tci
> build, which is already slow by nature, the logging is sufficient
> to push the test into timeout.

How does this get triggered because I added these:

# non-inline runs will trigger the duplicate instruction heuristics in libinsn.so
run-plugin-%-with-libinsn.so:
	$(call run-test, $@, \
	  $(QEMU) -monitor none -display none \
		  -chardev file$(COMMA)path=$@.out$(COMMA)id=output \
                  -plugin ../../plugin/libinsn.so$(COMMA)inline=on \
	    	  -d plugin -D $*-with-libinsn.so.pout \
		  $(QEMU_OPTS) $*)

to prevent the callback versions from being called for x86. The original
intent of the check was to detect failures due to cpu_io_recompile, see
e025d799af (tests/plugin: expand insn test to detect duplicate instructions)

>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> Irritatingly, it doesn't timeout locally, so I used staging to double-check:
>
> Fail: https://gitlab.com/qemu-project/qemu/-/jobs/4450754282#L5062
> Pass: https://gitlab.com/qemu-project/qemu/-/jobs/4450927108
> ---
>  tests/plugin/insn.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/tests/plugin/insn.c b/tests/plugin/insn.c
> index cd5ea5d4ae..9bd6e44f73 100644
> --- a/tests/plugin/insn.c
> +++ b/tests/plugin/insn.c
> @@ -19,7 +19,6 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
>  #define MAX_CPUS 8 /* lets not go nuts */
>  
>  typedef struct {
> -    uint64_t last_pc;
>      uint64_t insn_count;
>  } InstructionCount;
>  
> @@ -51,13 +50,7 @@ static void vcpu_insn_exec_before(unsigned int cpu_index, void *udata)
>  {
>      unsigned int i = cpu_index % MAX_CPUS;
>      InstructionCount *c = &counts[i];
> -    uint64_t this_pc = GPOINTER_TO_UINT(udata);
> -    if (this_pc == c->last_pc) {
> -        g_autofree gchar *out = g_strdup_printf("detected repeat execution @ 0x%"
> -                                                PRIx64 "\n", this_pc);
> -        qemu_plugin_outs(out);
> -    }
> -    c->last_pc = this_pc;
> +
>      c->insn_count++;
>  }


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro