linux-kernel - Re: [PATCH 07/24] xen/arm: Xen detection and shared

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Date:	Fri, 27 Jul 2012 15:51:25 +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 07/24] xen/arm: Xen detection and shared_info page
 mapping

On Fri, 2012-07-27 at 15:48 +0100, Stefano Stabellini wrote:
> On Fri, 27 Jul 2012, Ian Campbell wrote:
> > On Thu, 2012-07-26 at 16:33 +0100, Stefano Stabellini wrote:
> > > Check for a "/xen" node in the device tree, if it is present set
> > > xen_domain_type to XEN_HVM_DOMAIN and continue initialization.
> > > 
> > > Map the real shared info page using XENMEM_add_to_physmap with
> > > XENMAPSPACE_shared_info.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > > ---
> > >  arch/arm/xen/enlighten.c |   56 ++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 files changed, 56 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > > index d27c2a6..8c923af 100644
> > > --- a/arch/arm/xen/enlighten.c
> > > +++ b/arch/arm/xen/enlighten.c
> > > @@ -5,6 +5,9 @@
> > >  #include <asm/xen/hypervisor.h>
> > >  #include <asm/xen/hypercall.h>
> > >  #include <linux/module.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_irq.h>
> > > +#include <linux/of_address.h>
> > >  
> > >  struct start_info _xen_start_info;
> > >  struct start_info *xen_start_info = &_xen_start_info;
> > > @@ -33,3 +36,56 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
> > >  	return -ENOSYS;
> > >  }
> > >  EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
> > > +
> > > +/*
> > > + * == Xen Device Tree format ==
> > > + * - /xen node;
> > > + * - compatible "arm,xen";
> > > + * - one interrupt for Xen event notifications;
> > > + * - one memory region to map the grant_table.
> > > + */
> > > +static int __init xen_guest_init(void)
> > > +{
> > > +	int cpu;
> > > +	struct xen_add_to_physmap xatp;
> > > +	static struct shared_info *shared_info_page = 0;
> > > +	struct device_node *node;
> > > +
> > > +	node = of_find_compatible_node(NULL, NULL, "arm,xen");
> > > +	if (!node) {
> > > +		pr_info("No Xen support\n");
> > > +		return 0;
> > > +	}
> > 
> > This should either only print in the success case (to avoid spamming
> > everyone) or we need a little bit of infrastructure like on x86 so that
> > we print exactly one of:
> > 	"Booting natively on bearmetal"
> > 	"Booting paravirtualised on %s", hypervisor->name
> 
> This function is only going to be called once (actually it might be
> called twice with the change introduced by "xen/arm: Introduce
> xen_guest_init").

Once (or twice), per boot, per ARM system running Linux in the world...

Ian.

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