linux-kernel - Re: [PATCH v2 1/2] perf/x86/intel: Expose EPT-friendly PEBS for SPR and future models

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Date:   Thu, 22 Sep 2022 08:41:12 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Like Xu <like.xu.linux@...il.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Jim Mattson <jmattson@...gle.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 1/2] perf/x86/intel: Expose EPT-friendly PEBS for SPR
 and future models



On 2022-09-22 1:19 a.m., Like Xu wrote:
> From: Like Xu <likexu@...cent.com>
> 
> According to Intel SDM, the EPT-friendly PEBS is supported by all the
> platforms after ICX, ADL and the future platforms with PEBS format 5.
> 
> Currently the only in-kernel user of this capability is KVM, which has
> very limited support for hybrid core pmu, so ADL and its successors do
> not currently expose this capability. When both hybrid core and PEBS
> format 5 are present, KVM will decide on its own merits.
> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: linux-perf-users@...r.kernel.org
> Suggested-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Like Xu <likexu@...cent.com>


Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Thanks,
Kan

> ---
> V1 -> V2 Changelog:
> - the perf part should be a separate patch; (Kan)
> - apply PEBS format 5 to avoid patching every future model; (Kan)
> 
>  arch/x86/events/intel/core.c | 1 +
>  arch/x86/events/intel/ds.c   | 4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index 2db93498ff71..804540ba4599 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -6288,6 +6288,7 @@ __init int intel_pmu_init(void)
>  		x86_pmu.pebs_constraints = intel_spr_pebs_event_constraints;
>  		x86_pmu.extra_regs = intel_spr_extra_regs;
>  		x86_pmu.limit_period = spr_limit_period;
> +		x86_pmu.pebs_ept = 1;
>  		x86_pmu.pebs_aliases = NULL;
>  		x86_pmu.pebs_prec_dist = true;
>  		x86_pmu.pebs_block = true;
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index ba60427caa6d..4e937f685cdc 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -2253,8 +2253,10 @@ void __init intel_ds_init(void)
>  			x86_pmu.large_pebs_flags |= PERF_SAMPLE_TIME;
>  			break;
>  
> -		case 4:
>  		case 5:
> +			x86_pmu.pebs_ept = 1;
> +			fallthrough;
> +		case 4:
>  			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) {