linux-kernel - Re: perf with precise attribute kills all KVM based VMs

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Message-ID: <20120709145714.GF7298@redhat.com>
Date:	Mon, 9 Jul 2012 17:57:14 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	David Ahern <dsahern@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: perf with precise attribute kills all KVM based VMs

On Mon, Jul 09, 2012 at 05:54:42PM +0300, Gleb Natapov wrote:
> On Mon, Jul 09, 2012 at 05:51:29PM +0300, Avi Kivity wrote:
> > On 07/09/2012 05:49 PM, Peter Zijlstra wrote:
> > > On Mon, 2012-07-09 at 08:47 -0600, David Ahern wrote:
> > >> 
> > >> I found this testing changes to perf-kvm, but found the problem extends 
> > >> to just perf-record. With perf-record exclude_guest defaults to 1. See 
> > >> tools/perf/util/util.c, event_attr_init(). 
> > > 
> > > You lost me there.. so perf-record defaults to exclude_guest=1 (which
> > > would make the proposed patch I just send actually possible), but its
> > > still going *bang* ?
> > 
> > It's possible that the DS writes overshoot the MSR... or that there's a
> > bug somewhere.
> > 
> I hope it is the later, because we can do nothing with the former.
> 
Actually we can disable DS before guest entry.

--
			Gleb.
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