On Wed, Sep 7, 2022 at 11:00 PM Sandipan Das <sandipan.das@xxxxxxx> 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).
