linux-kernel - Re: [PATCH] KVM: VMX: Enable Notify VM exit

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Message-ID: <31218420-f20c-aa7f-089d-54e9fecf35aa@intel.com>
Date:   Tue, 3 Nov 2020 13:36:22 +0800
From:   Tao Xu <tao3.xu@...el.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     pbonzini@...hat.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, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH] KVM: VMX: Enable Notify VM exit


On 11/3/20 1:32 AM, Sean Christopherson wrote:
> On Mon, Nov 02, 2020 at 02:14:45PM +0800, Tao Xu wrote:
>> There are some cases that malicious virtual machines can cause CPU stuck
>> (event windows don't open up), e.g., infinite loop in microcode when
>> nested #AC (CVE-2015-5307). No event window obviously means no events,
>> e.g. NMIs, SMIs, and IRQs will all be blocked, may cause the related
>> hardware CPU can't be used by host or other VM.
>>
>> To resolve those cases, it can enable a notify VM exit if no
>> event window occur in VMX non-root mode for a specified amount of
>> time (notify window).
>>
>> Expose a module param for setting notify window, default setting it to
>> the time as 1/10 of periodic tick, and user can set it to 0 to disable
>> this feature.
>>
>> TODO:
>> 1. The appropriate value of notify window.
>> 2. Another patch to disable interception of #DB and #AC when notify
>> VM-Exiting is enabled.
>>
>> Co-developed-by: Xiaoyao Li <xiaoyao.li@...el.com>
>> Signed-off-by: Tao Xu <tao3.xu@...el.com>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> 
> Incorrect ordering, since you're sending the patch, you "handled" it last,
> therefore your SOB should come last, i.e.:
> 
>    Co-developed-by: Xiaoyao Li <xiaoyao.li@...el.com>
>    Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
>    Signed-off-by: Tao Xu <tao3.xu@...el.com>
> 
OK, I will correct this.