Messages in this thread | | | Date | Tue, 27 Feb 2024 10:38:16 +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 2024/2/27 2:57, Robin Murphy 写道: > On 19/02/2024 6:37 am, Yang Jialong 杨佳龙 wrote: >> >> >> 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). > > Now consider the other case below that, where "type" has not matched > anything registered, so "pmu" is NULL, and the event is then offered to > *every* registered PMU to see if anyone accepts it. Note that even CPU > PMUs don't always register as PERF_TYPE_RAW, and in particular arm_pmu > doesn't. > arm_pmu has flag PERF_PMU_CAP_EXTENDED_HW_TYPE.
From below command, we can say that generic events is related to the pmus with type PERF_TYPE_RAW. ~/real_kernel $ grep -nr "PERF_TYPE_HARDWARE" arch/ drivers/ |cut -d: -f1|xargs egrep -c "perf_pmu_register.*PERF_TYPE_RAW" arch/alpha/kernel/perf_event.c:1 arch/alpha/kernel/perf_event.c:1 arch/arc/kernel/perf_event.c:1 arch/csky/kernel/perf_event.c:1 arch/loongarch/kernel/perf_event.c:1 arch/loongarch/kernel/perf_event.c:1 arch/mips/kernel/perf_event_mipsxx.c:1 arch/mips/kernel/perf_event_mipsxx.c:1 arch/powerpc/perf/8xx-pmu.c:1 arch/powerpc/perf/core-fsl-emb.c:1 arch/powerpc/perf/core-book3s.c:1 arch/riscv/kvm/vcpu_pmu.c:0 arch/s390/kernel/perf_cpum_sf.c:1 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/sh/kernel/perf_event.c:1 arch/sh/kernel/perf_event.c:1 arch/sparc/kernel/perf_event.c:1 arch/x86/events/amd/ibs.c:0 arch/x86/events/intel/core.c:0 arch/x86/events/core.c:1 arch/xtensa/kernel/perf_event.c:1 drivers/perf/arm_pmu.c:0 drivers/perf/arm_pmu.c:0 drivers/perf/riscv_pmu.c:0 drivers/perf/riscv_pmu_legacy.c:1 drivers/perf/arm_pmuv3.c:0 drivers/perf/riscv_pmu_sbi.c:1
From this, we can say that generic events is related to the pmus with capability PERF_PMU_CAP_EXTENDED_HW_TYPE. ~/real_kernel $ grep -nr "PERF_TYPE_HARDWARE" arch/ drivers/ |cut -d: -f1|xargs grep -c "PERF_PMU_CAP_EXTENDED_HW_TYPE" arch/alpha/kernel/perf_event.c:0 arch/alpha/kernel/perf_event.c:0 arch/arc/kernel/perf_event.c:0 arch/csky/kernel/perf_event.c:0 arch/loongarch/kernel/perf_event.c:0 arch/loongarch/kernel/perf_event.c:0 arch/mips/kernel/perf_event_mipsxx.c:0 arch/mips/kernel/perf_event_mipsxx.c:0 arch/powerpc/perf/8xx-pmu.c:0 arch/powerpc/perf/core-fsl-emb.c:0 arch/powerpc/perf/core-book3s.c:0 arch/riscv/kvm/vcpu_pmu.c:0 arch/s390/kernel/perf_cpum_sf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/s390/kernel/perf_cpum_cf.c:0 arch/sh/kernel/perf_event.c:0 arch/sh/kernel/perf_event.c:0 arch/sparc/kernel/perf_event.c:0 arch/x86/events/amd/ibs.c:0 arch/x86/events/intel/core.c:0 arch/x86/events/core.c:1 arch/xtensa/kernel/perf_event.c:0 drivers/perf/arm_pmu.c:2 drivers/perf/arm_pmu.c:2 drivers/perf/riscv_pmu.c:0 drivers/perf/riscv_pmu_legacy.c:0 drivers/perf/arm_pmuv3.c:0 drivers/perf/riscv_pmu_sbi.c:0
**************************** Something bad belows: ~/real_kernel $ grep -nr "PERF_TYPE_HARDWARE" arch/ drivers/ |cut -d: -f1|xargs egrep -c "perf_pmu_register.*-1" arch/alpha/kernel/perf_event.c:0 arch/alpha/kernel/perf_event.c:0 arch/arc/kernel/perf_event.c:0 arch/csky/kernel/perf_event.c:0 arch/loongarch/kernel/perf_event.c:0 arch/loongarch/kernel/perf_event.c:0 arch/mips/kernel/perf_event_mipsxx.c:0 arch/mips/kernel/perf_event_mipsxx.c:0 arch/powerpc/perf/8xx-pmu.c:0 arch/powerpc/perf/core-fsl-emb.c:0 arch/powerpc/perf/core-book3s.c:0 arch/riscv/kvm/vcpu_pmu.c:0 arch/s390/kernel/perf_cpum_sf.c:0 arch/s390/kernel/perf_cpum_cf.c:2 arch/s390/kernel/perf_cpum_cf.c:2 arch/s390/kernel/perf_cpum_cf.c:2 arch/s390/kernel/perf_cpum_cf.c:2 arch/sh/kernel/perf_event.c:0 arch/sh/kernel/perf_event.c:0 arch/sparc/kernel/perf_event.c:0 arch/x86/events/amd/ibs.c:1 arch/x86/events/intel/core.c:0 arch/x86/events/core.c:0 arch/xtensa/kernel/perf_event.c:0 drivers/perf/arm_pmu.c:1 drivers/perf/arm_pmu.c:1 drivers/perf/riscv_pmu.c:0 drivers/perf/riscv_pmu_legacy.c:0 drivers/perf/arm_pmuv3.c:0 drivers/perf/riscv_pmu_sbi.c:0 The pmus::event_init handled PERF_TYPE_HARDWARE, but they was registered with perf_pmu_register(*, *, -1) without CAP_EXTENDED_HW_TPYE.
Can we unify them with PERF_TYPE_RAW or CAP_EXTENDED_HW_TYPE? Maybe the latter is well. So we can assign idr PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE a known pmu in perf_pmu_register just like: if(is_support_generic(pmu)) { ret = idr_alloc(&pmu_idr, pmu, PERF_TYPE_HARDWAR, PERF_TYPE_HARDWARE + 1, GFP_KERNEL); if(ret < 0) goto free_pdc; ret = idr_alloc(&pmu_idr, pmu, PERF_TYPE_HW_CACHE, PERF_TYPE_HW_CACHE + 1, GFP_KERNEL); if(ret < 0) goto free_pdc; } We will has a easy and rational way to write code in core.c::perf_init_event and perf_try_init_event about generic events. We can judge cpu < 0 in perf_try_init_event for uncore pmus. > Thanks, > Robin. >
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