Re: perf, H/W counters - ESX hosted VM

[Arun Sharma]

On Fri, May 27, 2011 at 01:33:54PM -0600, David Ahern wrote:
> 
> Has anyone successfully used perf within an ESX VM? dmesg shows a PMU is
> discovered:

Don't know about ESX. But in general, getting this right requires 
virtualizing PMU hardware (eg: save/restore PMU state on exit/entry
from the guest just the way the scheduler does for processes).

Also, the MSR read/writes to event-{select,count} registers must
be properly virtualized. Interrupt delivery (NMIs) is important
as well.

I suspect that MSR writes from the guest to the PMU related registers
are simply ignored in most virtual environments today.

 -Arun
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