linux-kernel - Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode

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Date:   Fri, 23 Jul 2021 15:11:59 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     "Hunter, Adrian" <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "coresight@...ts.linaro.org" <coresight@...ts.linaro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode

Hi Arnaldo,

On Wed, Jul 14, 2021 at 11:00:44AM -0300, Arnaldo Carvalho de Melo wrote:

[...]

> > So, I wasn't suggesting to add this info to the perf.data file header,
> > just to the in-memory 'struct perf_env'.
> > 
> > And also we should avoid unconditionally initializing things that we may
> > never need, please structure it as:
> 
> Oops, forgot these:
>  
> > static void perf_env__init_kernel_mode(struct perf_env *env)
> > {
> >        const char *arch = perf_env__raw_arch(env);
> > 
> >        if (!strncmp(arch, "x86_64", 6)   || !strncmp(arch, "aarch64", 7) ||
> >            !strncmp(arch, "arm64", 5)    || !strncmp(arch, "mips64", 6) ||
> >            !strncmp(arch, "parisc64", 8) || !strncmp(arch, "riscv64", 7) ||
> >            !strncmp(arch, "s390x", 5)    || !strncmp(arch, "sparc64", 7))
> >                kernel_is_64_bit = 1;
>                  env->kernel_is_64_bit = 1;
> >        else
> >                kernel_is_64_bit = 0;
>                  env->kernel_is_64_bit = 0;
> > }
> > 
> > 
> > void perf_env__init(struct perf_env *env)
> > {
> > 	...
> > 	env->kernel_is_64_bit = -1;
> > 	...
> > }
> > 
> > bool perf_env__kernel_is_64_bit(struct perf_env *env)
> > {
> > 	if (env->kernel_is_64_bit == -1)
> > 		perf_env__init_kernel_mode(env);
> > 
> > 	return env->kernel_is_64_bit;
> > }

Thanks a lot for the suggestion; this is much clear for me, will spin
new patch set by following it.

Sorry for slow response due to my bandwidth was occupied by a task in
hand.

Thanks,
Leo