Messages in this thread | | | Subject | Re: [PATCH v2 1/9] perf: Add EVENT_ATTR_ID to simplify event attributes | From | "liuqi (BA)" <> | Date | Wed, 2 Jun 2021 18:49:57 +0800 |
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Hi Will, On 2021/6/2 17:49, Will Deacon wrote: > On Wed, Jun 02, 2021 at 04:45:23PM +0800, liuqi (BA) wrote: >> >> Hi Will, >> >> Thanks for reviewing this patch. >> >> On 2021/6/1 21:10, Will Deacon wrote: >>> On Wed, May 19, 2021 at 05:51:51PM +0800, Qi Liu wrote: >>>> Similar EVENT_ATTR macros are defined in many PMU drivers, >>>> like HiSilicon PMU driver, Arm PMU driver, Arm SMMU PMU >>>> driver. So Add a generic macro to simplify code. >>>> >>>> Cc: Peter Zijlstra <peterz@infradead.org> >>>> Cc: Ingo Molnar <mingo@redhat.com> >>>> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> >>>> Cc: Mark Rutland <mark.rutland@arm.com> >>>> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> >>>> Signed-off-by: Qi Liu <liuqi115@huawei.com> >>>> --- >>>> include/linux/perf_event.h | 6 ++++++ >>>> kernel/events/core.c | 2 ++ >>>> 2 files changed, 8 insertions(+) >>>> >>>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >>>> index f5a6a2f..d0aa74e 100644 >>>> --- a/include/linux/perf_event.h >>>> +++ b/include/linux/perf_event.h >>>> @@ -1576,6 +1576,12 @@ static struct perf_pmu_events_attr _var = { \ >>>> .event_str = _str, \ >>>> }; >>>> +#define PMU_EVENT_ATTR_ID(_name, _id) \ >>>> + (&((struct perf_pmu_events_attr[]) { \ >>>> + { .attr = __ATTR(_name, 0444, perf_event_sysfs_show, NULL), \ >>>> + .id = _id, } \ >>>> + })[0].attr.attr) >>>> + >>>> #define PMU_FORMAT_ATTR(_name, _format) \ >>>> static ssize_t \ >>>> _name##_show(struct device *dev, \ >>>> diff --git a/kernel/events/core.c b/kernel/events/core.c >>>> index 0ac818b..330d9cc 100644 >>>> --- a/kernel/events/core.c >>>> +++ b/kernel/events/core.c >>>> @@ -13295,6 +13295,8 @@ ssize_t perf_event_sysfs_show(struct device *dev, struct device_attribute *attr, >>>> if (pmu_attr->event_str) >>>> return sprintf(page, "%s\n", pmu_attr->event_str); >>>> + else >>>> + return sprintf(page, "config=%#llx\n", pmu_attr->id); >>> >>> I think it's a really bad idea to hardcode this here. For example, I think >>> this patch series breaks user ABI for the SMMU PMU which used to print: >>> >>> "event=0x%02llx\n" >>> >>> and by the looks of it many of the other conversions are unsound too. >>> >> Got it, so I'll use pmu_attr->event_str here, for example, >> SMMU_EVENT_ATTR(cycles, "event=0x00") > > You could, but honestly I don't really see this being any better than the > current code. The advantage of using "event=0x%02llx\n" is that things are > consistent by construction and therefore userspace can parse the information > easily. We lose that if we just hardcode the string and it's error-prone to > extend. > > Will Got it, thanks. So how about adding a common macro like this:
#define PMU_EVENT_ATTR_ID(_name,_func, _id) \ (&((struct perf_pmu_events_attr[]) { \ { .attr = __ATTR(_name, 0444, _func, NULL), \ .id = _id, } \ })[0].attr.attr)
Drivers could define thir private macro, like SMMU_PMU_EVENT_ATTR, and use their private event_show() functions if they need, or use the common function perf_event_sysfs_show().
Thanks, Qi > . >
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