linux-kernel - Re: intel_pstate divide error with v3.13-rc4-256-gb7000ad

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Date:	Fri, 03 Jan 2014 23:06:21 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
CC:	Gleb Natapov <gleb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kashyap Chamarthy <kchamart@...hat.com>,
	Josh Boyer <jwboyer@...oraproject.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	"Richard W.M. Jones" <rjones@...hat.com>
Subject: Re: intel_pstate divide error with v3.13-rc4-256-gb7000ad

Il 03/01/2014 21:00, Dirk Brandewie ha scritto:
> +    case MSR_IA32_MPERF:
> +    case MSR_IA32_APERF:

These should never be accessed.  A KVM VM will always have
CPUID[06H].ECX = 0, and the Intel manual says that the MSRs are only
present if CPUID returns that value with bit 0 set.

I think the actual bug is that intel_pstate_init does not check the
feature bits in CPUID (either manually or via x86_match_cpu).

Paolo
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