Messages in this thread | | | Date | Mon, 19 Feb 2024 14:37:08 +0800 | Subject | Re: [PATCH] perf/arm_smmuv3: Omit the two judgements which done in framework | From | Yang Jialong 杨佳龙 <> |
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在 2024/2/10 0:32, Robin Murphy 写道: > On 2024-02-09 4:09 pm, Will Deacon wrote: >> On Thu, Dec 21, 2023 at 05:38:01PM +0800, JiaLong.Yang wrote: >>> 'event->attr.type != event->pmu->type' has been done in >>> core.c::perf_init_event() ,core.c::perf_event_modify_attr(), etc. >>> >>> This PMU is an uncore one. The core framework has disallowed >>> uncore-task events. So the judgement to event->cpu < 0 is no mean. >> >> It would be great to refer to the changes which added those checks to >> the perf core code. From reading the code myself, I can't convince myself >> that perf_try_init_event() won't call into the driver. >> >>> >>> The two judgements have been done in kernel/events/core.c >>> >>> Signed-off-by: JiaLong.Yang <jialong.yang@shingroup.cn> >>> --- >>> drivers/perf/arm_smmuv3_pmu.c | 8 -------- >>> 1 file changed, 8 deletions(-) >> >> It looks like _many_ perf drivers have these checks, so if they really >> aren't needed, we can clean this up bveyond SMMU. However, as I said >> above, I'm not quite convinced we can drop them. > > Right, I think the logic prevents events with a specific PMU type being > offered to other PMUs, but as far as I'm aware doesn't apply the other > way round to stop generic events (PERF_TYPE_HARDWARE etc.) being offered > to all PMUs, so it's those that system PMUs need to reject. > > It's been on my wishlist for a long time to have a capability flag to > say "I don't handle generic events, please only ever give me events of > my exact type" so we *can* truly factor this into the core.
It's core framework's responsible to differ generic events and others, or uncore pmu and core pmu. Here we have flag PERF_TYPE_HARDWARE, PERF_TYPE_HW_CACHE, PERF_PMU_CAP_EXTENDED_HW_TYPE doing this.
again: rcu_read_lock(); pmu = idr_find(&pmu_idr, type); rcu_read_unlock(); if (pmu) { if (event->attr.type != type && type != PERF_TYPE_RAW && !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE)) goto fail; /* generic event with no ability pmu */ This can avoid driver code (event->attr.type != event->pmu->type).
And, code: if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1)) { err = -EINVAL; goto err_pmu; } can promise not uncore-task event.
We should confirm that uncore event should be cpu >= 0.
> > Thanks, > Robin. >
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