Re: [PATCH v10 04/27] x86/fpu/xstate: Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set

[Yang, Weijiang]

On 5/8/2024 7:17 AM, Dave Hansen wrote:
> On 5/7/24 15:57, Sean Christopherson wrote:

[...]

> > My one request would be to change the WARN in os_xsave() to fire on CET_KERNEL,
> > not KERNEL_DYNAMIC, because it's specifically CET_KERNEL that is guest-only.
> > Future dynamic xfeatures could be guest-only, but they could also be dynamic for
> > some completely different reason.  That was my other hang-up with "DYNAMIC";
> > as-is, os_xsave() implies that it really truly is GUEST_ONLY.
> >
> > diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
> > index 83ebf1e1cbb4..2a1ff49ccfd5 100644
> > --- a/arch/x86/kernel/fpu/xstate.h
> > +++ b/arch/x86/kernel/fpu/xstate.h
> > @@ -185,8 +185,7 @@ static inline void os_xsave(struct fpstate *fpstate)
> >          WARN_ON_FPU(!alternatives_patched);
> >          xfd_validate_state(fpstate, mask, false);
> >   
> > -       WARN_ON_FPU(!fpstate->is_guest &&
> > -                   (mask & XFEATURE_MASK_KERNEL_DYNAMIC));
> > +       WARN_ON_FPU(!fpstate->is_guest && (mask & XFEATURE_MASK_CET_KERNEL));
> >   
> >          XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);
> Yeah, that would make a lot of sense.  We could add a more generic
> #define for it later if another feature gets added like this.

Thank you for getting alignment! I will change the code accordingly.