linux-kernel - Re: [PATCHv2 5/7] KVM: SVM: Add VNMI support in inject

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Message-ID: <b6030283-9d43-c3c3-9d58-4972cf7efb0d@amd.com>
Date:   Fri, 29 Jul 2022 19:25:45 +0530
From:   "Shukla, Santosh" <santosh.shukla@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 5/7] KVM: SVM: Add VNMI support in inject_nmi



On 7/29/2022 7:23 PM, Sean Christopherson wrote:
> On Fri, Jul 29, 2022, Shukla, Santosh wrote:
>> Hi Sean,
>>
>> On 7/21/2022 3:11 AM, Sean Christopherson wrote:
>>> On Sat, Jul 09, 2022, Santosh Shukla wrote:
>>>> +	++vcpu->stat.nmi_injections;
>>>> +	if (is_vnmi_enabled(svm)) {
>>>> +		vmcb = get_vnmi_vmcb(svm);
>>>> +		WARN_ON(vmcb->control.int_ctl & V_NMI_PENDING);
>>>
>>> Haven't read the spec, but based on the changelog I assume the flag doesn't get
>>> cleared until the NMI is fully delivered.  That means this WARN will fire if a
>>> VM-Exit occurs during delivery as KVM will re-inject the event, e.g. if KVM is
>>> using shadow paging and a #PF handle by KVM occurs during delivery.
>>>
>>
>> Right,.
>>
>>
>> For the above scenario i.e.. if VMEXIT happens during delivery of virtual NMI
>> then EXITINTINFO will be set accordingly and V_NMI_MASK is saved as 0.
>> hypervisor will re-inject event in next VMRUN.
>>
>> I just wanted to track above scenario,. I will replace it with pr_debug().
> 
> No, this is normal (albeit uncommon) behavior, don't print anything.  Even if it

Ok.

Thanks,
Santosh

> weren't normal behavior, pr_debug() is usually the wrong choice in KVM.