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

[Jim Mattson]

On Sun, Nov 1, 2020 at 10:14 PM Tao Xu <tao3.xu@xxxxxxxxx> 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@xxxxxxxxx>
> Signed-off-by: Tao Xu <tao3.xu@xxxxxxxxx>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>

Do you have test cases?