linux-kernel - Re: [PATCH 12/24] xen/arm: Introduce xen_guest

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Message-ID: <1343405479.25096.25.camel@zakaz.uk.xensource.com>
Date:	Fri, 27 Jul 2012 17:11:19 +0100
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"Tim (Xen.org)" <tim@....org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH 12/24] xen/arm: Introduce xen_guest_init

On Fri, 2012-07-27 at 16:54 +0100, Stefano Stabellini wrote:
> On Fri, 27 Jul 2012, Ian Campbell wrote:
> > On Thu, 2012-07-26 at 16:33 +0100, Stefano Stabellini wrote:
> > > We used to rely on a core_initcall to initialize Xen on ARM, however
> > > core_initcalls are actually called after early consoles are initialized.
> > > That means that hvc_xen.c is going to be initialized before Xen.
> > > 
> > > Given the lack of a better alternative, just call a new Xen
> > > initialization function (xen_guest_init) from xen_cons_init.
> > 
> > Can't we just arrange for this to be called super early on from
> > setup_arch? That's got to be better than calling it from some random
> > function which happens to get called early enough.
> 
> While I agree with you that an explicit call to xen_guest_init from
> generic code might be better, xen_cons_init is not just a random
> function: it is a console_initcall and therefore we know for sure that
> it is going be the first one to be called.

Initialising something != console in a console_initcall just because it
happens to be called early enough meets my definition of calling it from
a random place.

> In fact if we didn't want the PV console to work so early we could just
> rely on a core_initcall to initialize everything and we wouldn't have
> any issues.
> 
> 
> In any case if the ARM maintainers agree I could add a generic
> hypervisor initialization call the end of setup_arch.
> 
> 
> 
> > I presume that KVM is going to want some similarly early init hooks etc
> > and therefore ARM could benefit from the same sort of infrastructure as
> > is in arch/x86/include/asm/hypervisor.h?


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