Re: [PATCH v2 00/11] KVM in-guest performance monitoring

[David Ahern <daahern@cisco.com>]

On 06/13/2011 07:34 AM, Avi Kivity wrote:
> This patchset exposes an emulated version 1 architectural performance
> monitoring unit to KVM guests.  The PMU is emulated using perf_events,
> so the host kernel can multiplex host-wide, host-user, and the
> guest on available resources.

Any particular magic needed to try this patchset?

Host and guest both 64-bit, Fedora 14. Kernel for both is your 'kvm.git
next' with this patchset applied.

Host:
2 x Intel(R) Xeon(R) CPU           E5540  @ 2.53GHz
qemu-kvm git as of May 9.

Guest:
tried '-cpu host' and without a -cpu arg (so qemu-kvm default). In both
cases I get:

[    0.044999] CPU0: Intel(R) Xeon(R) CPU           E5540  @ 2.53GHz
stepping 05
[    0.046996] Performance Events: unsupported p6 CPU model 26 no PMU
driver, software events only.

David

> 
> Caveats:
> - counters that have PMI (interrupt) enabled stop counting after the
>   interrupt is signalled.  This is because we need one-shot samples
>   that keep counting, which perf doesn't support yet
> - some combinations of INV and CMASK are not supported
> - counters keep on counting in the host as well as the guest
> 
> perf maintainers: please consider the first three patches for merging (the
> first two make sense even without the rest).  If you're familiar with the Intel
> PMU, please review patch 5 as well - it effectively undoes all your work
> of abstracting the PMU into perf_events by unabstracting perf_events into what
> is hoped is a very similar PMU.
> 
> v2:
>  -  don't pass perf_event handler context to the callback; extract it via the
>     'event' parameter instead
>  -  RDPMC emulation and interception
>  -  CR4.PCE emulation
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