linux-kernel - Re: GPF in intel_pmu_lbr_reset() with qemu -cpu host

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Message-ID: <20140322085045.GA5535@minantech.com>
Date:	Sat, 22 Mar 2014 10:50:45 +0200
From:	Gleb Natapov <gleb@...nel.org>
To:	Venkatesh Srinivas <venkateshs@...gle.com>
Cc:	Peter Wu <peter@...ensteyn.nl>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: GPF in intel_pmu_lbr_reset() with qemu -cpu host

On Fri, Mar 21, 2014 at 12:04:32PM -0700, Venkatesh Srinivas wrote:
> On Fri, Mar 21, 2014 at 10:46 AM, Peter Wu <peter@...ensteyn.nl> wrote:
[skip]

> When -cpu host is used, qemu/kvm passed the host CPUID F/M/S to the
> guest. intel_pmu_cpu_*() -> intel_pmu_lbr_reset() uses rdmsr() /
> wrmsr(), rather than the safe variants; if KVM does not support the
> particular MSRs in question, you will see a #GP(0) there. See
> https://lkml.org/lkml/2014/3/13/453 for a similar bug other PMU code.
> 
When kernel is compiled with guest support all rdmsr()/wrmsr() become _safe(),
so the question for Peter is if his guest kernel has guest support enabled?
 
--
			Gleb.
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