linux-kernel - Re: [PATCH 1/1] KVM: x86: to track if L1 is running L2 VM

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Message-ID: <f0de2138-74f1-410a-f079-9d697ca6f145@oracle.com>
Date:   Fri, 12 Mar 2021 11:13:04 -0800
From:   Dongli Zhang <dongli.zhang@...cle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        linux-kernel@...r.kernel.org, joe.jin@...cle.com
Subject: Re: [PATCH 1/1] KVM: x86: to track if L1 is running L2 VM

Hi Paolo,

On 3/6/21 5:56 AM, Paolo Bonzini wrote:
> On 05/03/21 23:57, Dongli Zhang wrote:
>> The new per-cpu stat 'nested_run' is introduced in order to track if L1 VM
>> is running or used to run L2 VM.
>>
>> An example of the usage of 'nested_run' is to help the host administrator
>> to easily track if any L1 VM is used to run L2 VM. Suppose there is issue
>> that may happen with nested virtualization, the administrator will be able
>> to easily narrow down and confirm if the issue is due to nested
>> virtualization via 'nested_run'. For example, whether the fix like
>> commit 88dddc11a8d6 ("KVM: nVMX: do not use dangling shadow VMCS after
>> guest reset") is required.
>>
>> Cc: Joe Jin <joe.jin@...cle.com>
>> Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
...
> 
> Queued, thanks.
> 
> Paolo
>

While testing the most recent kvm tree, I did not find this patch queued
(debugfs entry for nested_run not available). Would you mind help confirm?

Thank you very much!

Dongli Zhang