Re: [PATCH v11 01/17] perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server

[Like Xu]

On 5/1/2022 1:25 am, Sean Christopherson wrote:
> On Fri, Dec 31, 2021, Like Xu wrote:
> > On 31/12/2021 2:13 am, Sean Christopherson wrote:
> > > On Fri, Dec 10, 2021, Like Xu wrote:
> > > > The new hardware facility supporting guest PEBS is only available on
> > > > Intel Ice Lake Server platforms for now. KVM will check this field
> > > > through perf_get_x86_pmu_capability() instead of hard coding the cpu
> > > > models in the KVM code. If it is supported, the guest PEBS capability
> > > > will be exposed to the guest.
> > >
> > > So what exactly is this new feature?  I've speed read the cover letter and a few
> > > changelogs and didn't find anything that actually explained when this feature does.
> >
> > Please check Intel SDM Vol3 18.9.5 for this "EPT-Friendly PEBS" feature.
> >
> > I assume when an unfamiliar feature appears in the patch SUBJECT,
> > the reviewer may search for the exact name in the specification.
>
> C'mon, seriously?  How the blazes am I supposed to know that the feature name
> is EPT-Friendly PEBS?  Or that it's even in the SDM (it's not in the year-old
> version of the SDM I currently have open) versus one of the many ISE docs?

You're right. The reviewer's time is valuable. Apologies for my wrong assumption.

> This is not hard.  Please spend the 30 seconds it takes to write a small blurb
> so that reviewers don't have to spend 5+ minutes wondering WTF this does.
>
>    Add support for EPT-Friendly PEBS, a new CPU feature that enlightens PEBS to
>    translate guest linear address through EPT, and facilitates handling VM-Exits
>    that occur when accessing PEBS records.  More information can be found in the
>    <date> release of Intel's SDM, Volume 3, 18.9.5 "EPT-Friendly PEBS".

Applied and thanks.