Re: [PATCH RFC 1/2] x86/entry_64: Add a separate unmitigated entry/exit path

[Waiman Long]

On 9/19/24 17:52, Pawan Gupta wrote:
> CPU mitigations are deployed system-wide, but usually not all of the
> userspace is malicious. Yet, they suffer from the performance impact
> of the mitigations. This all or nothing approach is due to lack of a
> way for kernel to know which userspace can be trusted and which cannot.
>
> For scenarios where an admin can decide which processes to trust, an
> interface to tell the kernel to possibly skip the mitigation would be
> useful.
>
> In preparation for kernel to be able to selectively apply mitigation
> per-process add a separate kernel entry/exit path that skips the
> mitigations.
>
> Originally-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>

For the current patch, not all x86 CPU vulnerability mitigations can be 
disabled. Maybe we should list the subset of mitigations that can be 
disabled.

Cheers,
Longman