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From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>
Cc: kvm@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: linux 3.13 guest crash with -cpu host
Date: Mon, 03 Feb 2014 15:07:33 +0100	[thread overview]
Message-ID: <52EFA2A5.7000203@redhat.com> (raw)
In-Reply-To: <20140203140601.GA24944@redhat.com>

Il 03/02/2014 15:06, Michael S. Tsirkin ha scritto:
>> Linux seems to be trying to read IA32_PERF_CAPABILITIES without checking the
>> PDCM flag (CPUID[1].ECX[15]).
>>
>> I can't see why this wasn't crashing before, though. That code seems to be old.
>>
>> 	 * v2 and above have a perf capabilities MSR
>> 	 */
>> 	if (version > 1) {
>> 		u64 capabilities;
>>
>> 		rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
>> 		x86_pmu.intel_cap.capabilities = capabilities;
>> 	}
>>
>> Where does the "v2 and above have a perf capabilities MSR" claim in the code
>> come from?
>
>
> But why doesn't it crash on baremetal?
> Probably baremetal simply returns 0 or something.
> Let me try ..

Because KVM doesn't implement the MSR, but your baremetal likely does.

Paolo


  reply	other threads:[~2014-02-03 14:07 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-02 20:59 linux 3.13 guest crash with -cpu host Michael S. Tsirkin
2014-02-03 12:58 ` Eduardo Habkost
2014-02-03 13:29   ` Peter Zijlstra
2014-02-21 21:14     ` [tip:perf/urgent] perf/x86: Correctly use FEATURE_PDCM tip-bot for Peter Zijlstra
2014-02-03 14:06   ` linux 3.13 guest crash with -cpu host Michael S. Tsirkin
2014-02-03 14:07     ` Paolo Bonzini [this message]
2014-02-03 14:42       ` Michael S. Tsirkin
2014-02-03 14:12     ` Peter Zijlstra
2014-02-03 14:19       ` Paolo Bonzini
2014-02-03 14:26         ` Peter Zijlstra
2014-02-03 14:28           ` Peter Zijlstra
2014-02-03 15:01             ` Paolo Bonzini
2014-02-03 14:45           ` Michael S. Tsirkin

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