On Tue, Jun 28, 2016 at 11:39:18AM +0800, xinhui wrote:
[snip]
> > > +{
> > > + struct lppaca *lp = &lppaca_of(cpu);
> > > +
> > > + if (unlikely(!(lppaca_shared_proc(lp) ||
> > > + lppaca_dedicated_proc(lp))))
> >
> > Do you want to detect whether we are running in a guest(ie. pseries
> > kernel) here? Then I wonder whether "machine_is(pseries)" works here.
> >
> I tried as you said yesterday. but .h file has dependencies.
> As you said, if we add #ifdef PPC_PSERIES, this is not a big problem. only
> powernv will be affected as they are built into same kernel img.
> I never said this it not a big problem ;-) The problem here is that we only need to detect the vcpu preemption in a guest, and there could be several ways we can detect whether the kernel is running in a guest. It's worthwhile to try find the best one for this. Besides, it's really better that you can make sure we are runing out of options before you introduce something like lppaca_dedicated_proc(). I have a feeling that yield_count is non-zero only if we are running in a guest, if so, we can use this and save several loads. But surely we need the confirmation from ppc maintainers. Regards, Boqun
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