Re: [PATCH RESEND 1/2] tools/perf: Add arch neutral function to choose event for perf kvm record

[Arnaldo Carvalho de Melo]

Em Mon, Jun 10, 2019 at 12:15:17PM +0530, Anju T Sudhakar escreveu:
> 'perf kvm record' uses 'cycles'(if the user did not specify any event) as
> the default event to profile the guest.
> This will not provide any proper samples from the guest incase of
> powerpc architecture, since in powerpc the PMUs are controlled by
> the guest rather than the host.
> 
> Patch adds a function to pick an arch specific event for 'perf kvm record',
> instead of selecting 'cycles' as a default event for all architectures.
> 
> For powerpc this function checks for any user specified event, and if there
> isn't any it returns invalid instead of proceeding with 'cycles' event.

Michael, Ravi, Maddy, could you please provide an Acked-by, Reviewed-by
or Tested-by?

- Arnaldo
 
> Signed-off-by: Anju T Sudhakar <anju@xxxxxxxxxxxxxxxxxx>
> ---
>  tools/perf/arch/powerpc/util/kvm-stat.c | 37 +++++++++++++++++++++++++
>  tools/perf/builtin-kvm.c                | 12 +++++++-
>  tools/perf/util/kvm-stat.h              |  2 +-
>  3 files changed, 49 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/arch/powerpc/util/kvm-stat.c b/tools/perf/arch/powerpc/util/kvm-stat.c
> index f9db341c47b6..66f8fe500945 100644
> --- a/tools/perf/arch/powerpc/util/kvm-stat.c
> +++ b/tools/perf/arch/powerpc/util/kvm-stat.c
> @@ -8,6 +8,7 @@
>  
>  #include "book3s_hv_exits.h"
>  #include "book3s_hcalls.h"
> +#include <subcmd/parse-options.h>
>  
>  #define NR_TPS 4
>  
> @@ -172,3 +173,39 @@ int cpu_isa_init(struct perf_kvm_stat *kvm, const char *cpuid __maybe_unused)
>  
>  	return ret;
>  }
> +
> +/*
> + * Incase of powerpc architecture, pmu registers are programmable
> + * by guest kernel. So monitoring guest via host may not provide
> + * valid samples. It is better to fail the "perf kvm record"
> + * with default "cycles" event to monitor guest in powerpc.
> + *
> + * Function to parse the arguments and return appropriate values.
> + */
> +int kvm_add_default_arch_event(int *argc, const char **argv)
> +{
> +	const char **tmp;
> +	bool event = false;
> +	int i, j = *argc;
> +
> +	const struct option event_options[] = {
> +		OPT_BOOLEAN('e', "event", &event, NULL),
> +		OPT_END()
> +	};
> +
> +	tmp = calloc(j + 1, sizeof(char *));
> +	if (!tmp)
> +		return -EINVAL;
> +
> +	for (i = 0; i < j; i++)
> +		tmp[i] = argv[i];
> +
> +	parse_options(j, tmp, event_options, NULL, 0);
> +	if (!event) {
> +		free(tmp);
> +		return -EINVAL;
> +	}
> +
> +	free(tmp);
> +	return 0;
> +}
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index dbb6f737a3e2..fe33b3ec55c9 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -1510,11 +1510,21 @@ static int kvm_cmd_stat(const char *file_name, int argc, const char **argv)
>  }
>  #endif /* HAVE_KVM_STAT_SUPPORT */
>  
> +int __weak kvm_add_default_arch_event(int *argc __maybe_unused,
> +					const char **argv __maybe_unused)
> +{
> +	return 0;
> +}
> +
>  static int __cmd_record(const char *file_name, int argc, const char **argv)
>  {
> -	int rec_argc, i = 0, j;
> +	int rec_argc, i = 0, j, ret;
>  	const char **rec_argv;
>  
> +	ret = kvm_add_default_arch_event(&argc, argv);
> +	if (ret)
> +		return -EINVAL;
> +
>  	rec_argc = argc + 2;
>  	rec_argv = calloc(rec_argc + 1, sizeof(char *));
>  	rec_argv[i++] = strdup("record");
> diff --git a/tools/perf/util/kvm-stat.h b/tools/perf/util/kvm-stat.h
> index 1403dec189b4..da38b56c46cb 100644
> --- a/tools/perf/util/kvm-stat.h
> +++ b/tools/perf/util/kvm-stat.h
> @@ -144,5 +144,5 @@ extern const int decode_str_len;
>  extern const char *kvm_exit_reason;
>  extern const char *kvm_entry_trace;
>  extern const char *kvm_exit_trace;
> -
> +extern int kvm_add_default_arch_event(int *argc, const char **argv);
>  #endif /* __PERF_KVM_STAT_H */
> -- 
> 2.17.2

-- 

- Arnaldo