linux-kernel - Re: [PATCH] perf/x86: fix RAPL rdmsrl

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Message-ID: <20140423200022.GJ8874@tassilo.jf.intel.com>
Date:	Wed, 23 Apr 2014 13:00:22 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Venkatesh Srinivas <venkateshs@...gle.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	Stephane Eranian <eranian@...gle.com>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>, mingo@...e.hu,
	zheng.z.yan@...el.com
Subject: Re: [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage

> > Acked-by: Borislav Petkov <bp@...e.de>
> 
> Brown-Paper-Bag-Worn-By: Venkatesh Srinivas <venkateshs@...gle.com>

Again the bug is really in KVM. We wouldn't need all this crap
if KVM didn't throw the bogus #GPs. I'm sure you missed plenty
of MSR accesses elsewhere, and it's a ticking time bomb.

If the VM lies to the kernel with the family-model you need to at 
least limit the consequences. KVM is spectacularly failing
to do that by throwing bogus #GPs.

The brown paper bad needs to be employed on the KVM code
(or better the bug be fixed there, by defaulting to not #GP
on unknown MSRs)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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