linux-kernel - Re: perf with precise attribute kills all KVM based VMs

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Message-ID: <5009EB16.1070809@gmail.com>
Date:	Fri, 20 Jul 2012 17:34:46 -0600
From:	David Ahern <dsahern@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Peter Zijlstra <peterz@...radead.org>, Avi Kivity <avi@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: perf with precise attribute kills all KVM based VMs

On 7/11/12 1:10 AM, Gleb Natapov wrote:
> Looks like Avi is right about the overshoot. Can you test something like this?
>
> 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;
>   }


Tested-by: David Ahern <dsahern@...il.com>

Peter's patch is required as well. It's the combination that fixes the 
problem.

David
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