From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Roedel, Joerg" <Joerg.Roedel@amd.com>
Subject: Re: [PATCH 1/3] perf, core: Introduce attrs to count in either host
 or guest mode
Date: Tue, 10 May 2011 16:59:02 +0200
Message-ID: <20110510145902.GA30996@amd.com>
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Cc: Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
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On Tue, May 10, 2011 at 10:45:46AM -0400, Peter Zijlstra wrote:
> On Tue, 2011-05-10 at 16:35 +0200, Joerg Roedel wrote:
> > +       /* Can't exclude counting in guest and in host mode */
> > +       if (attr.exclude_host && attr.exclude_guest)
> > +               return -EINVAL;
> 
> Why not?

By definition the counter won't count at all. The hardware just ignores
the bits if they are both set. My rationale here was that it does not
makes sense to setup a counter and exclude guest and host mode.

	Joerg