linux-kernel - Re: [PATCH] perf tools: fix guest mode monitoring on AMD

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Message-ID: <20120227182325.GA12302@8bytes.org>
Date:	Mon, 27 Feb 2012 19:23:25 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	acme@...hat.com, robert.richter@....com, peterz@...radead.org,
	mingo@...e.hu, gleb@...hat.com, joerg.roedel@....com
Subject: Re: [PATCH] perf tools: fix guest mode monitoring on AMD

On Mon, Feb 27, 2012 at 06:52:25PM +0100, Stephane Eranian wrote:
> Yeah, but that causes simple commands such as "perf stat -e cycles ls"
> to return 0 count.
> 
> So either you get a segfault or you get zero count. There is something
> else going on here...

Hmm, looks like the counters will not do any counting when EFER.SVME==0
and HO==1 or GO==1 is set in the counters :(
A solution would be to mask out these bits in the perf-ctrl register
when EFER.SVME=0

I'll try to come up with a fix soon.


	Joerg

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