Re: [PATCH V1 0/4] KVM vPMU support for x86

["Radim Krčmář" <rkrcmar@redhat.com>]

2014-11-03 12:23-0600, Wei Huang:
> 
> 
> On 11/03/2014 11:56 AM, Radim Krčmář wrote:
> > 2014-10-31 12:05-0400, Wei Huang:
> >> Currently KVM only supports vPMU for Intel platforms. This patch set 
> >> enable vPMU support for AMD platform by creating a common PMU
> >> interface for x86. The PMU calls from guest VMs are dispatched
> >> to corresponding functions defined in arch specific files.
> > 
> > The functionality looks good, so I just want verify the basic design:
> > why don't we emulate AMD PMU on Intel, and vice versa?
> > (Underlying PERF_COUNTs are identical in both.)
> 
> Thanks. The underlining perf counters can be very different between AMD
> and Intel. I think we can emulate AMD on Intel, or vice versa, for some
> common perfmon_events (such as PERF_COUNT_HW_CPU_CYCLES). But as soon as
> guest VMs access raw counters (see PERF_TYPE_RAW), we can't emulate them
> anymore.

Thanks, I guess raw counters are used more than I thought, so code
complexity would overshadow the gain of having at least something.

And then, there is the always perfect, "who cares" :)