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

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Date:   Wed, 9 Nov 2016 16:38:07 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     "Luck, Tony" <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        rt@...utronix.de, linux-edac@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 22/25] x86/mcheck: Do the init in one place

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

-- 
Regards/Gruss,
    Boris.

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