> > --- a/arch/x86/include/asm/switch_to.h
> > +++ b/arch/x86/include/asm/switch_to.h
> > @@ -71,9 +71,13 @@ static inline void update_task_stack(struct task_struct
> *task)
> > else
> > this_cpu_write(cpu_tss_rw.x86_tss.sp1, task->thread.sp0); #else
> > - /* Xen PV enters the kernel on the thread stack. */
> > - if (static_cpu_has(X86_FEATURE_XENPV))
> > + if (cpu_feature_enabled(X86_FEATURE_FRED)) {
> > + wrmsrl(MSR_IA32_FRED_RSP0,
> > + task_top_of_stack(task) + TOP_OF_KERNEL_STACK_PADDING);
>
> Urgh, I'm assuming this is a *fast* MSR ?
You're right, however that is another feature under development AFAIK.
Xin
