linux-kernel - Re: [PATCH v3 3/3] perf/x86/intel: Expose EPT-friendly PEBS for SPR and future models

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Message-ID: <42fc9103-bbd8-0482-e2fc-49589b6698b5@gmail.com>
Date:   Tue, 15 Nov 2022 15:16:28 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v3 3/3] perf/x86/intel: Expose EPT-friendly PEBS for SPR
 and future models

On 14/11/2022 8:46 pm, Peter Zijlstra wrote:
> On Wed, Nov 09, 2022 at 04:28:02PM +0800, 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.
> 
> Oh right; the whole ADL KVM trainwreck :/ What's the plan there?

As we know, our community doesn't really have a plan in terms of feature reception,
considering hyprid pmu doesn't have market share in the data center (where most KVM
users are, and the test farms), and KVM-based client hypervisor will actively 
control the
cpu that the KVM module initializes, and adds more trainwreck, so as of now I don't
have a timeline for vPMU on ADL+ (until there are noteworthy user complaints).

Please let me know if you and Kan have other input.

> 
>> 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>
>> ---
>> Nit: This change is proposed to be applied via the KVM tree.
> 
> Works for me;
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>