Re: [PATCH v3 10/21] KVM:x86: Add #CP support in guest exception classification

[Chao Gao]

On Thu, May 11, 2023 at 12:08:46AM -0400, Yang Weijiang wrote:
>Add handling for Control Protection (#CP) exceptions(vector 21).
>The new vector is introduced for Intel's Control-Flow Enforcement
>Technology (CET) relevant violation cases.
>

>Although #CP belongs contributory exception class, but the actual
>effect is conditional on CET being exposed to guest. If CET is not
>available to guest, #CP falls back to non-contributory and doesn't
>have an error code.

This sounds weird. is this the hardware behavior? If yes, could you
point us to where this behavior is documented?