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

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Message-ID: <20161109142221.3r6xwhkxbckuv3bh@linutronix.de>
Date:   Wed, 9 Nov 2016 15:22:21 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Borislav Petkov <bp@...en8.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 2016-11-08 10:23:02 [+0100], Borislav Petkov wrote:
> On Mon, Nov 07, 2016 at 09:12:24PM +0100, Borislav Petkov wrote:
> > On Mon, Nov 07, 2016 at 10:55:24AM -0800, Luck, Tony wrote:
> > > I don't think that helps as much as you'd like it to help (at
> > > least on Intel). A broadcast machine check that finds the boot
> > > CPU has set CR4[MCE]=1 is still going to end up in reset if any
> > > other CPU still has CR4[MCE]=0
> > 
> > By leaving/moving the setting of CR4 earlier on all cores, we'll
> > at least make the possible window for such potential resets a lot
> > smaller...
> 
> ... and in general, I'm still unsure about *why* we need this change for
> hotplug. bigeasy, can you please clarify first?

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.

> Thanks.

Sebastian