lkml.org 
[lkml]   [2022]   [Sep]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 4/4] KVM: x86/cpuid: Add AMD CPUID ExtPerfMonAndDbg leaf 0x80000022
On Wed, Sep 7, 2022 at 11:00 PM Sandipan Das <sandipan.das@amd.com> wrote:
> This is the suggested method for detecting the number of counters:
>
> If CPUID Fn8000_0022_EAX[PerfMonV2] is set, then use the new interface in
> CPUID Fn8000_0022_EBX to determine the number of counters.
>
> Else if CPUID Fn8000_0001_ECX[PerfCtrExtCore] is set, then six counters
> are available.
>
> Else, four legacy counters are available.
>
> There will be an APM update that will have this information in the
> "Detecting Hardware Support for Performance Counters" section.

Nonetheless, for compatibility with old software, Fn8000_0022_EBX can
never report less than four counters (or six, if
Fn8000_0001_ECX[PerfCtrExtCore] is set).

\
 
 \ /
  Last update: 2022-09-09 01:15    [W:0.068 / U:1.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site