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Date: Thu, 15 Apr 2010 12:09:28 +0300
From: Avi Kivity <avi@redhat.com>
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To: oerg Roedel <joro@8bytes.org>
CC: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Sheng Yang <sheng@linux.intel.com>, linux-kernel@vger.kernel.org,
       kvm@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>,
       Jes Sorensen <Jes.Sorensen@redhat.com>, Gleb Natapov <gleb@redhat.com>,
       Zachary Amsden <zamsden@redhat.com>, zhiteng.huang@intel.com,
       tim.c.chen@intel.com, Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH V3] perf & kvm: Enhance perf to collect KVM guest os	statistics
 from host side
References: <1902387910.2078.435.camel@ymzhang.sh.intel.com> <4BC588CF.5010507@redhat.com> <1902445479.2078.458.camel@ymzhang.sh.intel.com> <4BC6C8CD.1020801@redhat.com> <1902473858.2078.481.camel@ymzhang.sh.intel.com> <20100415090403.GA12697@8bytes.org>
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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.