linux-kernel - Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os statistics from host side

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Date:	Thu, 15 Apr 2010 12:09:28 +0300
From:	Avi Kivity <avi@...hat.com>
To:	oerg Roedel <joro@...tes.org>
CC:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sheng Yang <sheng@...ux.intel.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Jes Sorensen <Jes.Sorensen@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>, zhiteng.huang@...el.com,
	tim.c.chen@...el.com, Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os	statistics
 from host side

On 04/15/2010 12:04 PM, oerg Roedel wrote:
> On Mon, Apr 15, 2030 at 04:57:38PM +0800, Zhang, Yanmin wrote:
>
>    
>> I checked svm.c and it seems svm.c doesn't trigger a NMI to host if the NMI
>> happens in guest os. In addition, svm_complete_interrupts is called after
>> interrupt is enabled.
>>      
> Yes. The NMI is held pending by the hardware until the STGI instruction
> is executed.
> And for nested svm the svm_complete_interrupts function needs to be
> executed after the nested exit handling. Therefore it is done late on
> svm.
>    

So, we'd need something like the following:

    if (exit == NMI)
        __get_cpu_var(nmi_vcpu) = vcpu;

    stgi();

    if (exit == NMI) {
        while (!nmi_handled())
            cpu_relax();
        __get_cpu_var(nmi_vcpu) = NULL;
    }

and no code sharing betweem vmx and svm.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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