Re: [PATCH v2 1/7] perf/x86/core: Update x86_pmu.pebs_capable for ICELAKE_{X,D}

[Like Xu <like.xu.linux@gmail.com>]

On 15/8/2022 5:31 pm, Peter Zijlstra wrote:
> On Fri, Aug 12, 2022 at 09:52:13AM +0200, Paolo Bonzini wrote:
>> On 7/21/22 12:35, Like Xu wrote:
>>> From: Like Xu <likexu@tencent.com>
>>>
>>> Ice Lake microarchitecture with EPT-Friendly PEBS capability also support
>>> the Extended feature, which means that all counters (both fixed function
>>> and general purpose counters) can be used for PEBS events.
>>>
>>> Update x86_pmu.pebs_capable like SPR to apply PEBS_ALL semantics.
>>>
>>> Cc: Kan Liang <kan.liang@linux.intel.com>
>>> Fixes: fb358e0b811e ("perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server")
>>> Signed-off-by: Like Xu <likexu@tencent.com>
>>> ---
>>>    arch/x86/events/intel/core.c | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
>>> index 4e9b7af9cc45..e46fd496187b 100644
>>> --- a/arch/x86/events/intel/core.c
>>> +++ b/arch/x86/events/intel/core.c
>>> @@ -6239,6 +6239,7 @@ __init int intel_pmu_init(void)
>>>    	case INTEL_FAM6_ICELAKE_X:
>>>    	case INTEL_FAM6_ICELAKE_D:
>>>    		x86_pmu.pebs_ept = 1;
>>> +		x86_pmu.pebs_capable = ~0ULL;
>>>    		pmem = true;
>>>    		fallthrough;
>>>    	case INTEL_FAM6_ICELAKE_L:
>>
>> Peter, can you please ack this (you were not CCed on this KVM series but
>> this patch is really perf core)?
> 
> I would much rather see something like this; except I don't know if it
> is fully correct. I can never find what models support what... Kan do
> you know?

For guest PEBS, it's a minor optimization from 0d23dc34a7ce to reduce branch 
instructions:
https://lore.kernel.org/kvm/YKIqbph62oclxjnt@hirez.programming.kicks-ass.net/

> 
> 
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 2db93498ff71..b42c1beb9924 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -5933,7 +5933,6 @@ __init int intel_pmu_init(void)
>   		x86_pmu.pebs_aliases = NULL;
>   		x86_pmu.pebs_prec_dist = true;
>   		x86_pmu.lbr_pt_coexist = true;
> -		x86_pmu.pebs_capable = ~0ULL;
>   		x86_pmu.flags |= PMU_FL_HAS_RSP_1;
>   		x86_pmu.flags |= PMU_FL_PEBS_ALL;
>   		x86_pmu.get_event_constraints = glp_get_event_constraints;
> @@ -6291,7 +6290,6 @@ __init int intel_pmu_init(void)
>   		x86_pmu.pebs_aliases = NULL;
>   		x86_pmu.pebs_prec_dist = true;
>   		x86_pmu.pebs_block = true;
> -		x86_pmu.pebs_capable = ~0ULL;
>   		x86_pmu.flags |= PMU_FL_HAS_RSP_1;
>   		x86_pmu.flags |= PMU_FL_NO_HT_SHARING;
>   		x86_pmu.flags |= PMU_FL_PEBS_ALL;
> @@ -6337,7 +6335,6 @@ __init int intel_pmu_init(void)
>   		x86_pmu.pebs_aliases = NULL;
>   		x86_pmu.pebs_prec_dist = true;
>   		x86_pmu.pebs_block = true;
> -		x86_pmu.pebs_capable = ~0ULL;
>   		x86_pmu.flags |= PMU_FL_HAS_RSP_1;
>   		x86_pmu.flags |= PMU_FL_NO_HT_SHARING;
>   		x86_pmu.flags |= PMU_FL_PEBS_ALL;
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index ba60427caa6d..e2da643632b9 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -2258,6 +2258,7 @@ void __init intel_ds_init(void)
>   			x86_pmu.drain_pebs = intel_pmu_drain_pebs_icl;
>   			x86_pmu.pebs_record_size = sizeof(struct pebs_basic);
>   			if (x86_pmu.intel_cap.pebs_baseline) {
> +				x86_pmu.pebs_capable = ~0ULL;

The two features of "Extended PEBS (about pebs_capable)" and "Adaptive PEBS 
(about pebs_baseline)"
are orthogonal, although the two are often supported together.

>   				x86_pmu.large_pebs_flags |=
>   					PERF_SAMPLE_BRANCH_STACK |
>   					PERF_SAMPLE_TIME;