Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle path

[Quan Xu]

on 2017/8/29 22:39, Borislav Petkov wrote:
> On Tue, Aug 29, 2017 at 11:46:37AM +0000, Yang Zhang wrote:
> > Add poll in do_idle. For UP VM, if there are running task, it will not
> > goes into idle path, so we only enable poll in SMP VM.
> >
> > Signed-off-by: Yang Zhang <yang.zhang.wz@xxxxxxxxx>
> > Signed-off-by: Quan Xu <quan.xu0@xxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: Kyle Huey <me@xxxxxxxxxxxx>
> > Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> > Cc: Len Brown <len.brown@xxxxxxxxx>
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> >   arch/x86/kernel/process.c | 7 +++++++
> >   kernel/sched/idle.c       | 2 ++
> >   2 files changed, 9 insertions(+)
> >
> > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> > index 3ca1980..def4113 100644
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -332,6 +332,13 @@ void arch_cpu_idle(void)
> >   	x86_idle();
> >   }
> >   
> > +#if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT)
> > +void arch_cpu_idle_poll(void)
> > +{
> > +	paravirt_idle_poll();
> > +}
> > +#endif
> So this will get called on any system which has CONFIG_PARAVIRT enabled
> *even* if they're not running any guests.
>
> Huh?
ÂÂ Borislav ,
 yes, this will get called on any system which has CONFIG_PARAVIRT 
enabled.

 but if they are not running any guests, the callback is 
paravirt_nop() ,
ÂÂ IIUC which is as similar as the other paravirt_*, such as 
paravirt_pgd_free()..

Â- Quan