Messages in this thread Patch in this message | | | Date | Tue, 15 Aug 2023 10:35:09 +0100 | Subject | Re: [PATCH v5 2/6] perf arm64: Allow version comparisons of CPU IDs | From | John Garry <> |
| |
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. 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. >
This looks ok apart from a couple of comments, below.
Thanks, John
> Signed-off-by: James Clark <james.clark@arm.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;
Is there a reason to drop this check?
As I see, it is still checked in perf_pmu__getcpudid() -> get_cpuid_str() -> _get_cpuid(), and we don't zero the buf allocated in _get_cpuid()
> - > 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.
And what other values may be returned? If just 0/1, then can we have a bool return value?
> + * > + * 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) > +{ > + 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; > +}
| |