Re: [PATCH v5 6/7] x86/fpu/xstate: Introduce "guest-only" supervisor xfeature set

["Edgecombe, Rick P" <rick.p.edgecombe@intel.com>]

On Thu, 2025-04-10 at 15:24 +0800, Chao Gao wrote:
> From: Yang Weijiang <weijiang.yang@intel.com>
> 
> In preparation for upcoming CET virtualization support, the CET supervisor
> state will be added as a "guest-only" feature, since it is required only by
> KVM (i.e., guest FPUs). Establish the infrastructure for "guest-only"
> features.
> 
> Define a new XFEATURE_MASK_GUEST_SUPERVISOR mask to specify features that
> are enabled by default in guest FPUs but not in host FPUs. Specifically,
> for any bit in this set, permission is granted and XSAVE space is allocated
> during vCPU creation. Non-guest FPUs cannot enable guest-only features,
> even dynamically, and no XSAVE space will be allocated for them.
> 
> The mask is currently empty, but this will be changed by a subsequent
> patch.
> 
> Note that there is no plan to add "guest-only" user xfeatures, so the user
> default features remain unchanged.
> 
> Co-developed-by: Chao Gao <chao.gao@intel.com>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> ---

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>