From: David Ahern <dsahern@gmail.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: perf with precise attribute kills all KVM based VMs
Date: Wed, 11 Jul 2012 07:34:29 -0600 [thread overview]
Message-ID: <4FFD80E5.2010700@gmail.com> (raw)
In-Reply-To: <20120711095337.GJ23898@redhat.com>
On 7/11/12 3:53 AM, Gleb Natapov wrote:
> On Wed, Jul 11, 2012 at 11:49:47AM +0200, Peter Zijlstra wrote:
>> On Wed, 2012-07-11 at 10:10 +0300, Gleb Natapov wrote:
>>
>>> Looks like Avi is right about the overshoot. Can you test something like this?
I head to the airport in a few minutes; I'll try it out tonight or
tomorrow morning.
David
>>> diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
>>> index 166546e..5fb371a 100644
>>> --- a/arch/x86/kernel/cpu/perf_event_intel.c
>>> +++ b/arch/x86/kernel/cpu/perf_event_intel.c
>>> @@ -1374,8 +1374,11 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr)
>>> arr[0].msr = MSR_CORE_PERF_GLOBAL_CTRL;
>>> arr[0].host = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_guest_mask;
>>> arr[0].guest = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_host_mask;
>>> + arr[1].msr = MSR_IA32_PEBS_ENABLE;
>>> + arr[1].host = cpuc->pebs_enabled;
>>> + arr[1].guest = 0;
>>> + *nr = 2;
>>>
>>> - *nr = 1;
>>> return arr;
>>> }
>>
>>
>> You also need to clear TR, BTS, BTINT from MSR_IA32_DEBUGCTLMSR and
>> ideally you'd also clear MSR_IA32_DS_AREA so that any write will be a
>> proper NULL deref or such.
> Yes. With the patch above :pp modifier does not crash guest for me, but
> in theory it should since BTS are still written to DS. May be BTS writes do
> not overshoot guest entry. Will have to ask Intel for clarification.
>
> --
> Gleb.
>
next prev parent reply other threads:[~2012-07-11 13:34 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-09 14:12 perf with precise attribute kills all KVM based VMs David Ahern
2012-07-09 14:19 ` Gleb Natapov
2012-07-09 14:24 ` Peter Zijlstra
2012-07-09 14:36 ` Gleb Natapov
2012-07-09 14:39 ` Avi Kivity
2012-07-09 14:47 ` David Ahern
2012-07-09 14:49 ` Peter Zijlstra
2012-07-09 14:51 ` Avi Kivity
2012-07-09 14:54 ` Gleb Natapov
2012-07-09 14:57 ` Gleb Natapov
2012-07-09 14:59 ` Peter Zijlstra
2012-07-10 23:38 ` David Ahern
2012-07-11 7:10 ` Gleb Natapov
2012-07-11 9:49 ` Peter Zijlstra
2012-07-11 9:53 ` Gleb Natapov
2012-07-11 13:34 ` David Ahern [this message]
2012-07-12 4:11 ` David Ahern
2012-07-12 4:29 ` Gleb Natapov
2012-07-12 15:20 ` David Ahern
2012-07-12 16:06 ` Gleb Natapov
2012-07-12 16:13 ` Gleb Natapov
2012-07-12 16:58 ` Peter Zijlstra
2012-07-16 1:51 ` David Ahern
2012-07-15 8:07 ` Avi Kivity
2012-07-15 13:00 ` David Ahern
2012-07-15 13:03 ` Avi Kivity
2012-07-16 1:52 ` David Ahern
2012-07-16 2:19 ` David Ahern
2012-07-20 23:34 ` David Ahern
2012-07-22 9:52 ` Avi Kivity
2012-07-09 14:52 ` David Ahern
2012-07-09 14:58 ` David Ahern
2012-07-09 15:18 ` David Ahern
2012-07-09 14:47 ` Peter Zijlstra
2012-07-20 23:35 ` David Ahern
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