Does anyone know the scope of the MSR:
on SandyBridge? It is not listed in Table 35-11 of the Intel SDM Vol 3, where the scope of similar MSRs such as IA32_PERF_GLOBAL_CTRL is given.
The scope of the MSR is 'per hw thread'.
The MSR (38dh) is listed in table 35-2 as an architectural MSR but the scope isn't listed.
I'll check with the SDM owner to see if we can get the scope listed in the table.
Scope of IA32_FIXED_CTRx( starts at MSR addressing space 0x309) which is conrolled by IA32_PERF_FIXED_CTR_CTRL is per thread.
Moreover you can set 21 bit of IA32_PERFEVTSELx to enable counters on all logical processors thus mapping measurement to any thread which happens to be executed by logical processor.If bit 21 == 0 only specified in IA32_PERFEVTSELx logical processor's thread is measured.