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

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

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@tencent.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@infradead.org>
>> Cc: linux-perf-users@vger.kernel.org
>> Suggested-by: Kan Liang <kan.liang@linux.intel.com>
>> Signed-off-by: Like Xu <likexu@tencent.com>
>> Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
>> ---
>> Nit: This change is proposed to be applied via the KVM tree.
> 
> Works for me;
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>