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

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".

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