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Date:   Mon, 2 Nov 2020 09:32:37 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Tao Xu <tao3.xu@intel.com>
Cc:     pbonzini@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com,
        jmattson@google.com, joro@8bytes.org, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xiaoyao Li <xiaoyao.li@intel.com>
Subject: Re: [PATCH] KVM: VMX: Enable Notify VM exit
Message-ID: <20201102173236.GD21563@linux.intel.com>
References: <20201102061445.191638-1-tao3.xu@intel.com>
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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@intel.com>
> Signed-off-by: Tao Xu <tao3.xu@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.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@intel.com>
  Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
  Signed-off-by: Tao Xu <tao3.xu@intel.com>