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Message-ID: <295ae4dd-4734-42a0-be63-2d322f00c799@linux.ibm.com>
Date: Wed, 20 Aug 2025 10:09:07 +0200
From: Thomas Richter <tmricht@...ux.ibm.com>
To: Robin Murphy <robin.murphy@....com>, peterz@...radead.org,
mingo@...hat.com, will@...nel.org, mark.rutland@....com,
acme@...nel.org, namhyung@...nel.org,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com, kan.liang@...ux.intel.com
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev,
linux-csky@...r.kernel.org, loongarch@...ts.linux.dev,
linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
sparclinux@...r.kernel.org, linux-pm@...r.kernel.org,
linux-rockchip@...ts.infradead.org, dmaengine@...r.kernel.org,
linux-fpga@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
intel-xe@...ts.freedesktop.org, coresight@...ts.linaro.org,
iommu@...ts.linux.dev, linux-amlogic@...ts.infradead.org,
linux-cxl@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 18/19] perf: Introduce positive capability for raw events
On 8/19/25 15:15, Robin Murphy wrote:
> On 13/08/2025 6:01 pm, Robin Murphy wrote:
>> Only a handful of CPU PMUs accept PERF_TYPE_{RAW,HARDWARE,HW_CACHE}
>> events without registering themselves as PERF_TYPE_RAW in the first
>> place. Add an explicit opt-in for these special cases, so that we can
>> make life easier for every other driver (and probably also speed up the
>> slow-path search) by having perf_try_init_event() do the basic type
>> checking to cover the majority of cases.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>> ---
>>
>> A further possibility is to automatically add the cap to PERF_TYPE_RAW
>> PMUs in perf_pmu_register() to have a single point-of-use condition; I'm
>> undecided...
>> ---
>> arch/s390/kernel/perf_cpum_cf.c | 1 +
>> arch/s390/kernel/perf_pai_crypto.c | 2 +-
>> arch/s390/kernel/perf_pai_ext.c | 2 +-
>> arch/x86/events/core.c | 2 +-
>> drivers/perf/arm_pmu.c | 1 +
>> include/linux/perf_event.h | 1 +
>> kernel/events/core.c | 15 +++++++++++++++
>> 7 files changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
>> index 1a94e0944bc5..782ab755ddd4 100644
>> --- a/arch/s390/kernel/perf_cpum_cf.c
>> +++ b/arch/s390/kernel/perf_cpum_cf.c
>> @@ -1054,6 +1054,7 @@ static void cpumf_pmu_del(struct perf_event *event, int flags)
>> /* Performance monitoring unit for s390x */
>> static struct pmu cpumf_pmu = {
>> .task_ctx_nr = perf_sw_context,
>> + .capabilities = PERF_PMU_CAP_RAW_EVENTS,
>> .pmu_enable = cpumf_pmu_enable,
>> .pmu_disable = cpumf_pmu_disable,
>> .event_init = cpumf_pmu_event_init,
>> diff --git a/arch/s390/kernel/perf_pai_crypto.c b/arch/s390/kernel/perf_pai_crypto.c
>> index a64b6b056a21..b5b6d8b5d943 100644
>> --- a/arch/s390/kernel/perf_pai_crypto.c
>> +++ b/arch/s390/kernel/perf_pai_crypto.c
>> @@ -569,7 +569,7 @@ static const struct attribute_group *paicrypt_attr_groups[] = {
>> /* Performance monitoring unit for mapped counters */
>> static struct pmu paicrypt = {
>> .task_ctx_nr = perf_hw_context,
>> - .capabilities = PERF_PMU_CAP_SAMPLING,
>> + .capabilities = PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
>> .event_init = paicrypt_event_init,
>> .add = paicrypt_add,
>> .del = paicrypt_del,
>> diff --git a/arch/s390/kernel/perf_pai_ext.c b/arch/s390/kernel/perf_pai_ext.c
>> index 1261f80c6d52..bcd28c38da70 100644
>> --- a/arch/s390/kernel/perf_pai_ext.c
>> +++ b/arch/s390/kernel/perf_pai_ext.c
>> @@ -595,7 +595,7 @@ static const struct attribute_group *paiext_attr_groups[] = {
>> /* Performance monitoring unit for mapped counters */
>> static struct pmu paiext = {
>> .task_ctx_nr = perf_hw_context,
>> - .capabilities = PERF_PMU_CAP_SAMPLING,
>> + .capabilities = PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
>> .event_init = paiext_event_init,
>> .add = paiext_add,
>> .del = paiext_del,
>> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
>> index 789dfca2fa67..764728bb80ae 100644
>> --- a/arch/x86/events/core.c
>> +++ b/arch/x86/events/core.c
>> @@ -2697,7 +2697,7 @@ static bool x86_pmu_filter(struct pmu *pmu, int cpu)
>> }
>> static struct pmu pmu = {
>> - .capabilities = PERF_PMU_CAP_SAMPLING,
>> + .capabilities = PERF_PMU_CAP_SAMPLING | PERF_PMU_CAP_RAW_EVENTS,
>> .pmu_enable = x86_pmu_enable,
>> .pmu_disable = x86_pmu_disable,
>> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
>> index 72d8f38d0aa5..bc772a3bf411 100644
>> --- a/drivers/perf/arm_pmu.c
>> +++ b/drivers/perf/arm_pmu.c
>> @@ -877,6 +877,7 @@ struct arm_pmu *armpmu_alloc(void)
>> * specific PMU.
>> */
>> .capabilities = PERF_PMU_CAP_SAMPLING |
>> + PERF_PMU_CAP_RAW_EVENTS |
>> PERF_PMU_CAP_EXTENDED_REGS |
>> PERF_PMU_CAP_EXTENDED_HW_TYPE,
>> };
>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
>> index 183b7c48b329..c6ad036c0037 100644
>> --- a/include/linux/perf_event.h
>> +++ b/include/linux/perf_event.h
>> @@ -305,6 +305,7 @@ struct perf_event_pmu_context;
>> #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100
>> #define PERF_PMU_CAP_AUX_PAUSE 0x0200
>> #define PERF_PMU_CAP_AUX_PREFER_LARGE 0x0400
>> +#define PERF_PMU_CAP_RAW_EVENTS 0x0800
>> /**
>> * pmu::scope
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 71b2a6730705..2ecee76d2ae2 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -12556,11 +12556,26 @@ static inline bool has_extended_regs(struct perf_event *event)
>> (event->attr.sample_regs_intr & PERF_REG_EXTENDED_MASK);
>> }
>> +static bool is_raw_pmu(const struct pmu *pmu)
>> +{
>> + return pmu->type == PERF_TYPE_RAW ||
>> + pmu->capabilities & PERF_PMU_CAP_RAW_EVENTS;
>> +}
>> +
>> static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
>> {
>> struct perf_event_context *ctx = NULL;
>> int ret;
>> + /*
>> + * Before touching anything, we can safely skip:
>> + * - any event for a specific PMU which is not this one
>> + * - any common event if this PMU doesn't support them
>> + */
>> + if (event->attr.type != pmu->type &&
>> + (event->attr.type >= PERF_TYPE_MAX || is_raw_pmu(pmu)))
>
> Ah, that should be "!is_raw_pmu(pmu)" there (although it's not entirely the cause of the LKP report on the final patch.)
>
> Thanks,
> Robin.
>
>> + return -ENOENT;
>> +
>> if (!try_module_get(pmu->module))
>> return -ENODEV;
>>
>
>
Hi Robin,
what is the intention of that patch?
Can you explain that a bit more.
Thanks.
--
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
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