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

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Message-ID: <20201102173236.GD21563@linux.intel.com>
Date:   Mon, 2 Nov 2020 09:32:37 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Tao Xu <tao3.xu@...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 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>