Re: [PATCH 23/27] x86/fpu: Defer FPU state load until return to userspace

[Sebastian Andrzej Siewior]

On 2019-04-12 16:36:15 [+0200], Borislav Petkov wrote:
> On Wed, Apr 03, 2019 at 06:41:52PM +0200, Sebastian Andrzej Siewior wrote:
> > @@ -226,10 +236,9 @@ static void fpu__initialize(struct fpu *fpu)
> >  {
> >     WARN_ON_FPU(fpu != &current->thread.fpu);
> >  
> > +   set_thread_flag(TIF_NEED_FPU_LOAD);
> >     fpstate_init(&fpu->state);
> >     trace_x86_fpu_init_state(fpu);
> > -
> > -   trace_x86_fpu_activate_state(fpu);
> 
> That is called nowhere after this patch.

Isn't it called from fpu__clear()?

> Shouldn't it be called below, before fpregs_activate() because
> fpregs_activate() does trace_x86_fpu_regs_activated()?

Why? fpu__initialize() wipes the FPU state and starts from zero.
fpregs_mark_activate() on the other hand marks this FPU context is
currently active.

Sebastian