It leaks security sensitive information to userspace and corrupts the upper half of ESP because it lacks the equivalent of the espfix workaround.

On April 12, 2014 7:56:48 PM PDT, Andi Kleen <andi@firstfloor.org> wrote:
>"H. Peter Anvin" <hpa@zytor.com> writes:
>>
>> But yes, we can make it configurable, but the default should almost
>> certainly be off.
>
>Why? Either it works or it doesn't.
>
>If it works it doesn't make any sense to have a sysctl.
>
>-Andi

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