Subject: Re: [PATCH 12/13] powerpc/tracing: tracepoints for RTAS entry and exit

From: "Nicholas Piggin" <[email-masked]>
Date: Mon, 28 Nov 2022 12:54:19 +1000

On Sat Nov 19, 2022 at 1:07 AM AEST, Nathan Lynch wrote:
> Add two sets of tracepoints to be used around RTAS entry:
>
> * rtas_input/rtas_output, which emit the function name, its inputs,
>   the returned status, and any other outputs. These produce an API-level
>   record of OS<->RTAS activity.
>
> * rtas_ll_entry/rtas_ll_exit, which are lower-level and emit the
>   entire contents of the parameter block (aka rtas_args) on entry and
>   exit. Likely useful only for debugging.
>
> With uses of these tracepoints in do_enter_rtas() to be added in the
> following patch, examples of get-time-of-day and event-scan functions
> as rendered by trace-cmd (with some multi-line formatting manually
> imposed on the rtas_ll_* entries to avoid extremely long lines in the
> commit message):
>
> cat-36800 [059]  4978.518303: rtas_input:           get-time-of-day arguments:
> cat-36800 [059]  4978.518306: rtas_ll_entry:        token=3 nargs=0 nret=8
>                                                     params: [0]=0x00000000 [1]=0x00000000 [2]=0x00000000 [3]=0x00000000
>                                                             [4]=0x00000000 [5]=0x00000000 [6]=0x00000000 [7]=0x00000000
> 							    [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
> 							    [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
> cat-36800 [059]  4978.518366: rtas_ll_exit:         token=3 nargs=0 nret=8
>                                                     params: [0]=0x00000000 [1]=0x000007e6 [2]=0x0000000b [3]=0x00000001
> 						            [4]=0x00000000 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
> 							    [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
> 							    [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
> cat-36800 [059]  4978.518366: rtas_output:          get-time-of-day status: 0, other outputs: 2022 11 1 0 14 8 772648000
>
> kworker/39:1-336   [039]  4982.731623: rtas_input:           event-scan arguments: 4294967295 0 80484920 2048
> kworker/39:1-336   [039]  4982.731626: rtas_ll_entry:        token=6 nargs=4 nret=1
>                                                              params: [0]=0xffffffff [1]=0x00000000 [2]=0x04cc1a38 [3]=0x00000800
> 							             [4]=0x00000000 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
> 								     [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
> 								     [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
> kworker/39:1-336   [039]  4982.731676: rtas_ll_exit:         token=6 nargs=4 nret=1
>                                                              params: [0]=0xffffffff [1]=0x00000000 [2]=0x04cc1a38 [3]=0x00000800
> 							             [4]=0x00000001 [5]=0x0000000e [6]=0x00000008 [7]=0x2e0dac40
> 								     [8]=0x00000000 [9]=0x00000000 [10]=0x00000000 [11]=0x00000000
> 								     [12]=0x00000000 [13]=0x00000000 [14]=0x00000000 [15]=0x00000000
> kworker/39:1-336   [039]  4982.731677: rtas_output:          event-scan status: 1, other outputs:
>
> Signed-off-by: Nathan Lynch <[email-masked]>
> ---
>  arch/powerpc/include/asm/trace.h | 116 +++++++++++++++++++++++++++++++
>  1 file changed, 116 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/trace.h b/arch/powerpc/include/asm/trace.h
> index 08cd60cd70b7..e7a301c9eb95 100644
> --- a/arch/powerpc/include/asm/trace.h
> +++ b/arch/powerpc/include/asm/trace.h
> @@ -119,6 +119,122 @@ TRACE_EVENT_FN_COND(hcall_exit,
>  );
>  #endif
>  
> +#ifdef CONFIG_PPC_RTAS
> +
> +#include <asm/rtas-types.h>
> +
> +/*
> + * Since stop-self is how CPUs go offline on RTAS platforms,
> + * these tracepoints are conditional.
> + */
> +
> +TRACE_EVENT_CONDITION(rtas_input,
> +
> +	TP_PROTO(struct rtas_args *rtas_args, const char *name),
> +
> +	TP_ARGS(rtas_args, name),
> +
> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
> +
> +	TP_STRUCT__entry(
> +		__field(__u32, nargs)
> +		__string(name, name)
> +		__dynamic_array(__u32, inputs, be32_to_cpu(rtas_args->nargs))
> +	),
> +
> +	TP_fast_assign(
> +		__entry->nargs = be32_to_cpu(rtas_args->nargs);
> +		__assign_str(name, name);
> +		be32_to_cpu_array(__get_dynamic_array(inputs), rtas_args->args, __entry->nargs);
> +	),
> +
> +	TP_printk("%s arguments: %s", __get_str(name),
> +		  __print_array(__get_dynamic_array(inputs), __entry->nargs, 4)
> +	)
> +);
> +
> +TRACE_EVENT_CONDITION(rtas_output,
> +
> +	TP_PROTO(struct rtas_args *rtas_args, const char *name),
> +
> +	TP_ARGS(rtas_args, name),
> +
> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
> +
> +	TP_STRUCT__entry(
> +		__field(__u32, nr_other)
> +		__field(__s32, status)
> +		__string(name, name)
> +		__dynamic_array(__u32, other_outputs, be32_to_cpu(rtas_args->nret) - 1)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->nr_other = be32_to_cpu(rtas_args->nret) - 1;
> +		__entry->status = be32_to_cpu(rtas_args->rets[0]);
> +		__assign_str(name, name);
> +		be32_to_cpu_array(__get_dynamic_array(other_outputs),
> +				  &rtas_args->rets[1], __entry->nr_other);
> +	),
> +
> +	TP_printk("%s status: %d, other outputs: %s", __get_str(name), __entry->status,
> +		  __print_array(__get_dynamic_array(other_outputs),
> +				__entry->nr_other, 4)
> +	)
> +);
> +
> +DECLARE_EVENT_CLASS(rtas_parameter_block,
> +
> +	TP_PROTO(struct rtas_args *rtas_args),
> +
> +	TP_ARGS(rtas_args),
> +
> +	TP_STRUCT__entry(
> +		__field(u32, token)
> +		__field(u32, nargs)
> +		__field(u32, nret)
> +		__array(__u32, params, 16)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->token = be32_to_cpu(rtas_args->token);
> +		__entry->nargs = be32_to_cpu(rtas_args->nargs);
> +		__entry->nret = be32_to_cpu(rtas_args->nret);
> +		be32_to_cpu_array(__entry->params, rtas_args->args, ARRAY_SIZE(rtas_args->args));
> +	),
> +
> +	TP_printk("token=%u nargs=%u nret=%u params:"
> +		  " [0]=0x%08x [1]=0x%08x [2]=0x%08x [3]=0x%08x"
> +		  " [4]=0x%08x [5]=0x%08x [6]=0x%08x [7]=0x%08x"
> +		  " [8]=0x%08x [9]=0x%08x [10]=0x%08x [11]=0x%08x"
> +		  " [12]=0x%08x [13]=0x%08x [14]=0x%08x [15]=0x%08x",

You could justify these since you went to the trouble to format them
nicely. Not a big deal though.

Reviewed-by: Nicholas Piggin <[email-masked]>

> +		  __entry->token, __entry->nargs, __entry->nret,
> +		  __entry->params[0], __entry->params[1], __entry->params[2], __entry->params[3],
> +		  __entry->params[4], __entry->params[5], __entry->params[6], __entry->params[7],
> +		  __entry->params[8], __entry->params[9], __entry->params[10], __entry->params[11],
> +		  __entry->params[12], __entry->params[13], __entry->params[14], __entry->params[15]
> +	)
> +);
> +
> +DEFINE_EVENT_CONDITION(rtas_parameter_block, rtas_ll_entry,
> +
> +	TP_PROTO(struct rtas_args *rtas_args),
> +
> +	TP_ARGS(rtas_args),
> +
> +	TP_CONDITION(cpu_online(raw_smp_processor_id()))
> +);
> +
> +DEFINE_EVENT_CONDITION(rtas_parameter_block, rtas_ll_exit,
> +
> +	TP_PROTO(struct rtas_args *rtas_args),
> +
> +	TP_ARGS(rtas_args),
> +
> +	TP_CONDITION(cpu_online(raw_smp_processor_id()))
> +);
> +
> +#endif /* CONFIG_PPC_RTAS */
> +
>  #ifdef CONFIG_PPC_POWERNV
>  extern int opal_tracepoint_regfunc(void);
>  extern void opal_tracepoint_unregfunc(void);
> -- 
> 2.37.1