Messages in this thread | | | Date | Wed, 16 Aug 2023 11:15:54 +0100 | Subject | Re: [PATCH v5 2/6] perf arm64: Allow version comparisons of CPU IDs | From | John Garry <> |
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On 16/08/2023 10:12, James Clark wrote: > > > On 15/08/2023 10:35, John Garry wrote: >> 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() >> > > Ah yes, now if all the files fail to open or read then buf will be > uninitialized. I make it so that it will return EINVAL unless the > fgets() succeeds, but I don't think we need to add the strtoul() back in?
Right, I don't think that the strtoul() is required.
> >>> - >>> 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? >> > > I don't think that's best for consistency. All the other CPU ID > comparison functions return the strcmp style return values which is the > reverse of booleans. We could change them all to bool, but it would be a > big change, and they'd still have strcmp in the name which suggests > -1/0/1 return values (although -1 is never used here). > > I will add to the comment that 1 is returned for a comparison failure > thought. That is missing.
ok, fine.
> >>> + * >>> + * 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; >>> +} >>
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