Re: [PATCH 22/25] x86/mcheck: Do the init in one place

[Sebastian Andrzej Siewior]

On 2016-11-09 16:38:07 [+0100], Borislav Petkov wrote:
> On Wed, Nov 09, 2016 at 03:22:21PM +0100, Sebastian Andrzej Siewior wrote:
> > I want to get rid of non-symmetrical part and the arch hook which should
> > be part of the hp notifier itself. I wouldn't be too much afraid about
> > the when point in time when the notifier runs: It is the *first*
> > notifier that will be invoked on the target CPU. This is only a few
> > lines after the old hook. Nothing else long delaying should be invoked.
> 
> So I'm not sure *everything* mcheck_cpu_init() does should be in hotplug
> and toggle on and off. For example, we should set CR4.MCE once during
> init and that's it. Not turn it on and off. It would be pretty pointless
> IMO.
> 
> That's why the hotplug callback mce_disable_cpu() doesn't fiddle with
> CR4 - it only clears the bits in MCi_CTL. And I think we should remain
> that way.

The behaviour was not changed - it was only reorganized to keep in one
spot.

> The initial, one-time enabling of MCE features per core should be done
> only once per boot and that's it.

It is. You still want this in your hotplug code in case someone replaces
(physically) your CPU (say a larger NUMA box).

Sebastian