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SubjectRe: [PATCHES] Fix 'perf top' breakage on architectures not providing get_cpuid() Re: perf top for arm64?
On Wed, Dec 11, 2019 at 10:33:19AM -0300, Arnaldo Carvalho de Melo wrote:
> So can you take a look at the two patches below and provide me Acked-by
> and/or Reviewed-by and/or Tested-by?

I just gave this a spin. With vanilla v5.5-rc1 perf top behaves as John
reported, and with these applied atop perf works as expected:

Tested-by: Mark Rutland <mark.rutland@arm.com>

From scaning the code, the only other user of get_cpuid() that ends up
giving up is perf kvm, but AFAICT that never supported arm64, so that
looks sound to me:

Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> From 53c6cde6a71a1a9283763bd2e938b229b50c2cd5 Mon Sep 17 00:00:00 2001
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> Date: Wed, 11 Dec 2019 10:09:24 -0300
> Subject: [PATCH 1/2] perf arch: Make the default get_cpuid() return compatible
> error
>
> Some of the functions calling get_cpuid() propagate back the error it
> returns, and all are using errno (positive) values, make the weak
> default get_cpuid() function return ENOSYS to be consistent and to allow
> checking if this is an arch not providing this function or if a provided
> one is having trouble getting the cpuid, to decide if the warning should
> be provided to the user or just a debug message should be emitted.
>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: John Garry <john.garry@huawei.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Link: https://lkml.kernel.org/n/tip-lxwjr0cd2eggzx04a780ffrv@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
> tools/perf/util/header.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index becc2d109423..4d39a75551a0 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -850,7 +850,7 @@ int __weak strcmp_cpuid_str(const char *mapcpuid, const char *cpuid)
> */
> int __weak get_cpuid(char *buffer __maybe_unused, size_t sz __maybe_unused)
> {
> - return -1;
> + return ENOSYS; /* Not implemented */
> }
>
> static int write_cpuid(struct feat_fd *ff,
> --
> 2.21.0
>
> From c6c6a3e2eb6982e37294abcac389effd298cf730 Mon Sep 17 00:00:00 2001
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> Date: Wed, 11 Dec 2019 10:21:59 -0300
> Subject: [PATCH 2/2] perf top: Do not bail out when perf_env__read_cpuid()
> returns ENOSYS
>
> 'perf top' stopped working on hw architectures that do not provide a
> get_cpuid() implementation and thus fallback to the weak get_cpuid()
> default function.
>
> This is done because at annotation time we may need it in the arch
> specific annotation init routine, but that is only being used by arches
> that do provide a get_cpuid() implementation:
>
> $ find tools/ -name "*.[ch]" | xargs grep 'evlist->env'
> tools/perf/builtin-top.c: top.evlist->env = &perf_env;
> tools/perf/util/evsel.c: return evsel->evlist->env;
> tools/perf/util/s390-cpumsf.c: sf->machine_type = s390_cpumsf_get_type(session->evlist->env->cpuid);
> tools/perf/util/header.c: session->evlist->env = &header->env;
> tools/perf/util/sample-raw.c: const char *arch_pf = perf_env__arch(evlist->env);
> $
>
> $ find tools/perf/arch -name "*.[ch]" | xargs grep -w get_cpuid
> tools/perf/arch/x86/util/auxtrace.c: ret = get_cpuid(buffer, sizeof(buffer));
> tools/perf/arch/x86/util/header.c:get_cpuid(char *buffer, size_t sz)
> tools/perf/arch/powerpc/util/header.c:get_cpuid(char *buffer, size_t sz)
> tools/perf/arch/s390/util/header.c: * Implementation of get_cpuid().
> tools/perf/arch/s390/util/header.c:int get_cpuid(char *buffer, size_t sz)
> tools/perf/arch/s390/util/header.c: if (buf && get_cpuid(buf, 128))
> $
>
> For 'report' or 'script', i.e. tools working on perf.data files, that is
> setup while reading the header, its just top that needs to explicitely
> read it at tool start.
>
> Reported-by: John Garry <john.garry@huawei.com>
> Analysed-by: Jiri Olsa <jolsa@kernel.org>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Link: https://lkml.kernel.org/n/tip-lxwjr0cd2eggzx04a780ffrv@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
> tools/perf/builtin-top.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index dc80044bc46f..795e353de095 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -1568,9 +1568,13 @@ int cmd_top(int argc, const char **argv)
> */
> status = perf_env__read_cpuid(&perf_env);
> if (status) {
> - pr_err("Couldn't read the cpuid for this machine: %s\n",
> - str_error_r(errno, errbuf, sizeof(errbuf)));
> - goto out_delete_evlist;
> + /*
> + * Some arches do not provide a get_cpuid(), so just use pr_debug, otherwise
> + * warn the user explicitely.
> + */
> + eprintf(status == ENOSYS ? 1 : 0, verbose,
> + "Couldn't read the cpuid for this machine: %s\n",
> + str_error_r(errno, errbuf, sizeof(errbuf)));
> }
> top.evlist->env = &perf_env;
>
> --
> 2.21.0
>

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