Many PMUs do not support common hardware/cache/etc. events and only
handle their own PMU-specific events. Since this only depends on
matching the event and PMU types, it's a prime candidate for a core
capability to save more event_init boilerplate in drivers.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 5 +++++
2 files changed, 6 insertions(+)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..983201f21dd2 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -291,6 +291,7 @@ struct perf_event_pmu_context;
#define PERF_PMU_CAP_NO_EXCLUDE 0x0040
#define PERF_PMU_CAP_AUX_OUTPUT 0x0080
#define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100
+#define PERF_PMU_CAP_NO_COMMON_EVENTS 0x0200
struct perf_output_handle;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f0f0f71213a1..7ad80826c218 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11649,6 +11649,11 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
struct perf_event_context *ctx = NULL;
int ret;
+ /* Short-circuit if we know the PMU won't want this event */
+ if (pmu->capabilities & PERF_PMU_CAP_NO_COMMON_EVENTS &&
+ event->attr.type != pmu->type)
+ return -ENOENT;
+
if (!try_module_get(pmu->module))
return -ENODEV;
--
2.39.2.101.g768bb238c484.dirty
在 2024/3/13 1:34, Robin Murphy 写道:
> Many PMUs do not support common hardware/cache/etc. events and only
> handle their own PMU-specific events. Since this only depends on
> matching the event and PMU types, it's a prime candidate for a core
> capability to save more event_init boilerplate in drivers.
>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
> include/linux/perf_event.h | 1 +
> kernel/events/core.c | 5 +++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d2a15c0c6f8a..983201f21dd2 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -291,6 +291,7 @@ struct perf_event_pmu_context;
> #define PERF_PMU_CAP_NO_EXCLUDE 0x0040
> #define PERF_PMU_CAP_AUX_OUTPUT 0x0080
> #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100
> +#define PERF_PMU_CAP_NO_COMMON_EVENTS 0x0200
>
> struct perf_output_handle;
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f0f0f71213a1..7ad80826c218 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11649,6 +11649,11 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
> struct perf_event_context *ctx = NULL;
> int ret;
>
> + /* Short-circuit if we know the PMU won't want this event */
> + if (pmu->capabilities & PERF_PMU_CAP_NO_COMMON_EVENTS &&
> + event->attr.type != pmu->type)
> + return -ENOENT;
> +
/*
* PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE
* are often aliases for PERF_TYPE_RAW.
*/
type = event->attr.type;
if (type == PERF_TYPE_HARDWARE || type == PERF_TYPE_HW_CACHE) {
type = event->attr.config >> PERF_PMU_TYPE_SHIFT;
if (!type) {
type = PERF_TYPE_RAW;
} else {
extended_type = true;
event->attr.config &= PERF_HW_EVENT_MASK;
}
}
again:
rcu_read_lock();
pmu = idr_find(&pmu_idr, type);
rcu_read_unlock();
if (pmu) {
Above code tells me it's possible that 'pmu->type != event->attr.type'
is true when event->attr.type equals to PERF_TYPE_HARDWARE or
PERF_TYPE_HW_CACHE, and pmu->type should equal to event->attr.config >>
PERF_PMU_TYPE_SHIFT.
We find the target pmu by event->attr.config >> PERF_PMU_TYPE_SHIFT.
Code added discard this option.
And code tells me that no try. Target PMU is doubtless.
> if (!try_module_get(pmu->module))
> return -ENODEV;
>
On 2024-03-14 8:09 am, Yang Jialong 杨佳龙 wrote:
>
>
> 在 2024/3/13 1:34, Robin Murphy 写道:
>> Many PMUs do not support common hardware/cache/etc. events and only
>> handle their own PMU-specific events. Since this only depends on
>> matching the event and PMU types, it's a prime candidate for a core
>> capability to save more event_init boilerplate in drivers.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>> include/linux/perf_event.h | 1 +
>> kernel/events/core.c | 5 +++++
>> 2 files changed, 6 insertions(+)
>>
>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
>> index d2a15c0c6f8a..983201f21dd2 100644
>> --- a/include/linux/perf_event.h
>> +++ b/include/linux/perf_event.h
>> @@ -291,6 +291,7 @@ struct perf_event_pmu_context;
>> #define PERF_PMU_CAP_NO_EXCLUDE 0x0040
>> #define PERF_PMU_CAP_AUX_OUTPUT 0x0080
>> #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100
>> +#define PERF_PMU_CAP_NO_COMMON_EVENTS 0x0200
>> struct perf_output_handle;
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index f0f0f71213a1..7ad80826c218 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -11649,6 +11649,11 @@ static int perf_try_init_event(struct pmu
>> *pmu, struct perf_event *event)
>> struct perf_event_context *ctx = NULL;
>> int ret;
>> + /* Short-circuit if we know the PMU won't want this event */
>> + if (pmu->capabilities & PERF_PMU_CAP_NO_COMMON_EVENTS &&
>> + event->attr.type != pmu->type)
>> + return -ENOENT;
>> +
>
> /*
> * PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE
> * are often aliases for PERF_TYPE_RAW.
> */
> type = event->attr.type;
> if (type == PERF_TYPE_HARDWARE || type == PERF_TYPE_HW_CACHE) {
> type = event->attr.config >> PERF_PMU_TYPE_SHIFT;
> if (!type) {
> type = PERF_TYPE_RAW;
> } else {
> extended_type = true;
> event->attr.config &= PERF_HW_EVENT_MASK;
> }
> }
>
> again:
> rcu_read_lock();
> pmu = idr_find(&pmu_idr, type);
> rcu_read_unlock();
> if (pmu) {
> Above code tells me it's possible that 'pmu->type != event->attr.type'
> is true when event->attr.type equals to PERF_TYPE_HARDWARE or
> PERF_TYPE_HW_CACHE, and pmu->type should equal to event->attr.config >>
> PERF_PMU_TYPE_SHIFT.
>
> We find the target pmu by event->attr.config >> PERF_PMU_TYPE_SHIFT.
And if that PMU doesn't actually support PERF_TYPE_HARDWARE or
PERF_TYPE_HW_CACHE then it would reject the event, if the very next
lines didn't already do that:
if (event->attr.type != type && type != PERF_TYPE_RAW &&
!(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
goto fail;
Either way it should be clear that there's no change of functionality
here since the flow into perf_try_init_event() itself is untouched.
> Code added discard this option.
It would already be nonsensical for a driver to advertise
PERF_PMU_CAP_EXTENDED_HW_TYPE to say it supports extended hardware
events, but then reject all hardware events with a "event->attr.type !=
pmu->type" check in its event_init. Reworking the latter condition into
PERF_PMU_CAP_NO_COMMON_EVENTS doesn't change that.
Thanks,
Robin.
>
> And code tells me that no try. Target PMU is doubtless.
>
>
>
>
>> if (!try_module_get(pmu->module))
>> return -ENODEV;
>
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