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From: Josh Boyer <jwboyer@fedoraproject.org>
To: Gleb Natapov <gleb@kernel.org>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Dirk Brandewie <dirk.brandewie@gmail.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"cpufreq@vger.kernel.org" <cpufreq@vger.kernel.org>,
	Linux PM list <linux-pm@vger.kernel.org>,
	"Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
	Kashyap Chamarthy <kchamart@redhat.com>,
	"Richard W.M. Jones" <rjones@redhat.com>
Subject: Re: intel_pstate divide error with v3.13-rc4-256-gb7000ad
Date: Fri, 27 Dec 2013 08:46:25 -0500	[thread overview]
Message-ID: <CA+5PVA60GSC0tTLJWLtVqb5eTPMzrszxtoBnUP8B_Q_60=oGyw@mail.gmail.com> (raw)
In-Reply-To: <20131227124749.GE10961@minantech.com>

On Fri, Dec 27, 2013 at 7:47 AM, Gleb Natapov <gleb@kernel.org> wrote:
> On Fri, Dec 27, 2013 at 12:24:22PM +0000, One Thousand Gnomes wrote:
>> On Tue, 24 Dec 2013 21:36:01 +0530
>> Viresh Kumar <viresh.kumar@linaro.org> wrote:
>>
>> > Adding Dirk..
>> >
>> > On 24 December 2013 20:06, Josh Boyer <jwboyer@fedoraproject.org> wrote:
>> > > Hi All,
>> > >
>> > > We've had a report [1] that the pstate driver causes KVM guests to
>> > > fail to boot because of a divide error.  See the backtrace below.
>> > >
>> > >     4.839784] Intel P-state driver initializing.
>> > > [    4.859972] Intel pstate controlling: cpu 0
>> > > [    4.867653] cpufreq: __cpufreq_add_dev: ->get() failed
>> >
>> > After a call to ->init(), ->get() is supposed to work.
>> > @Dirk: Any idea why it failed?
>> >
>> > And then I don't know what made this divide by zero to happen :)
>>
>> > > [    4.878127] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
>>
>> Emulator bug perhaps ?
>>
> KVM does not emulate P-states at all. intel_pstate_init() calls
> intel_pstate_msrs_not_valid() before printing "Intel P-state driver
> initializing."  which suppose to fail since it checks that two reads of
> MSR_IA32_APERF return different values, but KVM does not emulate this msr
> at all, so both calls should return zero (KVM suppose to inject #GP, all rdmsrl
> are patched to be rdmsrl_safe in a guest).
>
> Anything interesting in host dmesg? Is it reproducible?

Seems reproducible.  I forgot to link to the actual bug in my original
report, but you can find it here:

https://bugzilla.redhat.com/show_bug.cgi?id=1046317

Adding Richard and Kashyap on CC.

josh

  reply	other threads:[~2013-12-27 13:46 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-24 14:36 intel_pstate divide error with v3.13-rc4-256-gb7000ad Josh Boyer
2013-12-24 16:06 ` Viresh Kumar
2013-12-27 12:24   ` One Thousand Gnomes
2013-12-27 12:47     ` Gleb Natapov
2013-12-27 13:46       ` Josh Boyer [this message]
2013-12-27 14:15         ` Kashyap Chamarthy
2013-12-27 14:34           ` Richard W.M. Jones
2013-12-27 16:52           ` Gleb Natapov
2013-12-27 17:01             ` Gleb Natapov
2013-12-27 17:17               ` Richard W.M. Jones
2013-12-27 17:17               ` Kashyap Chamarthy
2013-12-27 21:51                 ` Rafael J. Wysocki
2013-12-29 12:12                   ` Kashyap Chamarthy
2013-12-29 15:04                     ` Rafael J. Wysocki
2013-12-30 14:58                       ` Kashyap Chamarthy
2013-12-31  2:07                         ` Rafael J. Wysocki
2014-01-03 17:30                           ` Dirk Brandewie
2014-01-03 18:04                             ` Gleb Natapov
2014-01-03 20:00                               ` Dirk Brandewie
2014-01-03 22:06                                 ` Paolo Bonzini
2014-01-06 17:18                                   ` Dirk Brandewie
2014-01-07 16:11                                     ` Gleb Natapov
2014-01-03 22:46                               ` Rafael J. Wysocki
2014-01-04  8:35                                 ` Paolo Bonzini
2014-01-04 14:38                                   ` Rafael J. Wysocki
2014-01-04 17:38                                     ` Paolo Bonzini
2014-01-04 17:48                                       ` Gleb Natapov
2014-01-04 21:38                                         ` Rafael J. Wysocki
2014-01-06 11:20                                           ` Paolo Bonzini
2014-01-06 11:37                                             ` Rafael J. Wysocki
2014-01-06 18:40                                               ` Dirk Brandewie
2013-12-27 14:35   ` Rafael J. Wysocki

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