Re: [PATCH 01/19] x86/fpu: Extend prctl() with guest permissions

[Thomas Gleixner]

On Tue, Dec 07 2021 at 19:03, Yang Zhong wrote:
> Similar to native permissions this doesn't actually enable the
> permitted feature. KVM is expected to install a larger kernel buffer
> and enable the feature when detecting the intention from the guest.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Jing Liu <jing2.liu@xxxxxxxxx>
> Signed-off-by: Yang Zhong <yang.zhong@xxxxxxxxx>
> ---
> (To Thomas) We change the definition of xstate_get_guest_group_perm()
> from xstate.h to api.h since this will be called by KVM.

No.

There is absolutely no need for that. After creating a vCPU the
permissions are frozen and readily available via
vcpu->arch.guest_fpu.perm.

Thanks,

        tglx