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SubjectRe: [PATCH] KVM: VMX: Enable Notify VM exit

On 11/3/20 6:53 AM, Jim Mattson wrote:
> On Sun, Nov 1, 2020 at 10:14 PM 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 <>
>> Signed-off-by: Tao Xu <>
>> Signed-off-by: Xiaoyao Li <>
> Do you have test cases?
Not yet, because we are waiting real silicon to do some test. I should
add RFC next time before I test it in hardware.

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