Re: [PATCH 08/11] perf tool: precise mode requires exclude_guest

From: David Ahern
Date: Thu Aug 02 2012 - 12:07:13 EST


Hi Peter:

On 7/25/12 11:50 PM, Gleb Natapov wrote:
On Wed, Jul 25, 2012 at 10:35:46PM +0200, Peter Zijlstra wrote:
On Tue, 2012-07-24 at 18:15 +0200, Robert Richter wrote:
thanks for this hint.

On AMD cpus precise_ip maps to IBS, which does not support hardware
options as perfctrs do. Thus, following attr flags are not supported:

exclude_user, exclude_kernel, exclude_host, exclude_guest

Counting in guest mode is possible with IBS, but not the exclusion of
a certain mode. If precise_ip counting is enabled on AMD we may not
set the exclude_guest flag.

IIRC we have SVM enter/exit hooks in kvm/perf already, we could use
those to implement exclude_guest for IBS.

Now I've been trying to find the patches that introduced that, but I'm
failing horridly. Gleb, got us a pointer here?
The commit is 144d31e6, but it introduces hook that is used on VMX only.
SVM does not need it to implement guest/host only counters since it
has HW support for that in the PMU.

Any updates?

David

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