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Message-ID: <47a32410-d9ca-627b-e8a3-f64d4a1ea95f@oracle.com>
Date: Mon, 14 Aug 2023 14:07:18 +0100
From: John Garry <john.g.garry@...cle.com>
To: James Clark <james.clark@....com>,
linux-perf-users@...r.kernel.org, irogers@...gle.com,
renyu.zj@...ux.alibaba.com
Cc: Will Deacon <will@...nel.org>, Mike Leach <mike.leach@...aro.org>,
Leo Yan <leo.yan@...aro.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Kan Liang <kan.liang@...ux.intel.com>,
Nick Forrington <nick.forrington@....com>,
Kajol Jain <kjain@...ux.ibm.com>,
Eduard Zingerman <eddyz87@...il.com>,
Sohom Datta <sohomdatta1@...il.com>,
Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org
Subject: Re: [PATCH v5 2/6] perf arm64: Allow version comparisons of CPU IDs
On 11/08/2023 15:39, James Clark wrote:
> Currently variant and revision fields are masked out of the MIDR so
> it's not possible to compare different versions of the same CPU.
> In a later commit a workaround will be removed just for N2 r0p3, so
> enable comparisons on version.
>
> This has the side effect of changing the MIDR stored in the header of
> the perf.data file to no longer have masked version fields.
Did you consider adding a raw version of _get_cpuid(), which returns the
full MIDR just for the purpose of caller strcmp_cpuid_str()?
I can't comment on how it will be called in relation to
strcmp_cpuid_str(), as I am unsure whether strcmp_cpuid_str() should be
just in arch arm64 code - see comment on later patch.
It also
> affects the lookups in mapfile.csv, but as that currently only has
> zeroed version fields, it has no actual effect. The mapfile.csv
> documentation also states to zero the version fields, so unless this
> isn't done it will continue to have no effect.
>
> Signed-off-by: James Clark <james.clark@....com>
> ---
> tools/perf/arch/arm64/util/header.c | 64 ++++++++++++++++++++++-------
> 1 file changed, 50 insertions(+), 14 deletions(-)
>
> diff --git a/tools/perf/arch/arm64/util/header.c b/tools/perf/arch/arm64/util/header.c
> index 80b9f6287fe2..8f74e801e1ab 100644
> --- a/tools/perf/arch/arm64/util/header.c
> +++ b/tools/perf/arch/arm64/util/header.c
> @@ -1,3 +1,6 @@
> +#include <linux/kernel.h>
> +#include <linux/bits.h>
> +#include <linux/bitfield.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <perf/cpumap.h>
> @@ -10,14 +13,12 @@
>
> #define MIDR "/regs/identification/midr_el1"
> #define MIDR_SIZE 19
> -#define MIDR_REVISION_MASK 0xf
> -#define MIDR_VARIANT_SHIFT 20
> -#define MIDR_VARIANT_MASK (0xf << MIDR_VARIANT_SHIFT)
> +#define MIDR_REVISION_MASK GENMASK(3, 0)
> +#define MIDR_VARIANT_MASK GENMASK(23, 20)
>
> static int _get_cpuid(char *buf, size_t sz, struct perf_cpu_map *cpus)
> {
> const char *sysfs = sysfs__mountpoint();
> - u64 midr = 0;
> int cpu;
>
> if (!sysfs || sz < MIDR_SIZE)
> @@ -44,21 +45,11 @@ static int _get_cpuid(char *buf, size_t sz, struct perf_cpu_map *cpus)
> }
> fclose(file);
>
> - /* Ignore/clear Variant[23:20] and
> - * Revision[3:0] of MIDR
> - */
> - midr = strtoul(buf, NULL, 16);
> - midr &= (~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK));
> - scnprintf(buf, MIDR_SIZE, "0x%016lx", midr);
> /* got midr break loop */
> break;
> }
>
> perf_cpu_map__put(cpus);
> -
> - if (!midr)
> - return EINVAL;
> -
> return 0;
> }
>
> @@ -99,3 +90,48 @@ char *get_cpuid_str(struct perf_pmu *pmu)
>
> return buf;
> }
> +
> +/*
> + * Return 0 if idstr is a higher or equal to version of the same part as
> + * mapcpuid.
> + *
> + * Therefore, if mapcpuid has 0 for revision and variant then any version of
> + * idstr will match as long as it's the same CPU type.
> + */
> +int strcmp_cpuid_str(const char *mapcpuid, const char *idstr)
should we check implementator and other fields as a sanity check?
> +{
> + u64 map_id = strtoull(mapcpuid, NULL, 16);
> + char map_id_variant = FIELD_GET(MIDR_VARIANT_MASK, map_id);
> + char map_id_revision = FIELD_GET(MIDR_REVISION_MASK, map_id);
> + u64 id = strtoull(idstr, NULL, 16);
> + char id_variant = FIELD_GET(MIDR_VARIANT_MASK, id);
> + char id_revision = FIELD_GET(MIDR_REVISION_MASK, id);
> + u64 id_fields = ~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK);
> +
> + /* Compare without version first */
> + if ((map_id & id_fields) != (id & id_fields))
> + return 1;
> +
> + /*
> + * ID matches, now compare version.
> + *
> + * Arm revisions (like r0p0) are compared here like two digit semver
> + * values eg. 1.3 < 2.0 < 2.1 < 2.2. The events json file with the
> + * highest matching version is used.
> + *
> + * r = high value = 'Variant' field in MIDR
> + * p = low value = 'Revision' field in MIDR
> + *
> + */
> + if (id_variant > map_id_variant)
> + return 0;
> +
> + if (id_variant == map_id_variant && id_revision >= map_id_revision)
> + return 0;
> +
> + /*
> + * variant is less than mapfile variant or variants are the same but
> + * the revision doesn't match. Return no match.
> + */
> + return 1;
> +}
Thanks,
John
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