linux-kernel - Re: [Xen-devel] [PATCH v6 1/4] arm: introduce psci_smp

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Message-ID: <alpine.DEB.2.02.1304241911420.4180@kaball.uk.xensource.com>
Date:	Wed, 24 Apr 2013 19:13:15 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
CC:	Ian Campbell <Ian.Campbell@...rix.com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"arnd@...db.de" <arnd@...db.de>,
	"marc.zyngier@....com" <marc.zyngier@....com>,
	"will.deacon@....com" <will.deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Xen-devel] [PATCH v6 1/4] arm: introduce psci_smp_ops

On Mon, 22 Apr 2013, Nicolas Pitre wrote:
> > I think the key thing that non-Xen folks aren't aware of is that
> > although Xen passes the majority of the underlying hardware to the dom0
> > kernel to manage one of the few things it does not expose to guests
> > (where "guests" includes dom0) is the SMP topology of the underlying system.
> 
> I suspect it is unlikely to pass on the DT information about the CCI 
> either.  Which means that, in the case that started this thread, the 
> smp_init function needed by MCPM will simply return false and the next 
> priority in the list i.e. plain PSCI will be initialized instead.
> 
> I don't forsee the need to poke at the hardware directly within 
> ->smp_init, not since everything is moving to DT now.
> 
> Sure there are ways to screw up Xen support from within this hook, but 
> that can be achieved in many other places.  Will Xen take over every 
> possible hooks in the kernel to prevent that from happening?
> 
> So please let's not cry wolf needlessly.

OK, you convinced me :-)
I'll drop the patch.
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