linux-kernel - Re: [Xen-devel] [PATCH WIP 2/6] xen/arm: Introduce xen_guest

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Date:	Fri, 13 Jul 2012 17:38:34 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"Tim (Xen.org)" <tim@....org>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: [Xen-devel] [PATCH WIP 2/6] xen/arm: Introduce xen_guest_init

On Mon, 9 Jul 2012, Konrad Rzeszutek Wilk wrote:
> On Fri, Jun 22, 2012 at 05:14:41PM +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.
> > 
> > xen_guest_init has to be arch independant, so write both an ARM and an
> > x86 implementation. The x86 implementation is currently empty because we
> > can be sure that xen_hvm_guest_init is called early enough.
> > 
> > Probably we can get rid of this as soon as we have better DT support.
> 
> What is DT?
> 
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > ---
> >  arch/arm/xen/enlighten.c  |   12 ++++++++----
> >  arch/x86/xen/enlighten.c  |    8 ++++++++
> >  drivers/tty/hvc/hvc_xen.c |    3 +++
> >  include/xen/xen.h         |    2 ++
> >  4 files changed, 21 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index 7d76962..e1c2e4d 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -127,12 +127,16 @@ out:
> >  }
> >  EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
> >  
> > -void __ref xen_hvm_init_shared_info(void)
> > +static void __init xen_hvm_init_shared_info(void)
> >  {
> >  	int cpu;
> >  	struct xen_add_to_physmap xatp;
> >  	static struct shared_info *shared_info_page = 0;
> >  
> > +	/* already setup */
> > +	if (shared_info_page != 0 && HYPERVISOR_shared_info == shared_info_page)
> > +		return;
> > +
> >  	if (!shared_info_page)
> >  		shared_info_page = (struct shared_info *)
> >  			get_zeroed_page(GFP_KERNEL);
> > @@ -161,11 +165,11 @@ void __ref xen_hvm_init_shared_info(void)
> >  		per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
> >  	}
> >  }
> > +core_initcall(xen_hvm_init_shared_info);
> >  
> > -static int __init xen_hvm_guest_init(void)
> > +int __init xen_guest_init(void)
> >  {
> >  	xen_hvm_init_shared_info();
> >  	return 0;
> 
> Don't you want to do:
> 	return xen_hvm_init_shared_info();
> 
> why do we need to return int?

We don't need to, but it might be a good idea to propagate setup errors.


> >  }
> > -
> > -core_initcall(xen_hvm_guest_init);
> > +EXPORT_SYMBOL(xen_guest_init);
> > diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> > index 1f92865..0bad7b5 100644
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -1420,4 +1420,12 @@ const struct hypervisor_x86 x86_hyper_xen_hvm __refconst = {
> >  	.init_platform		= xen_hvm_guest_init,
> >  };
> >  EXPORT_SYMBOL(x86_hyper_xen_hvm);
> > +
> > +int __init xen_guest_init(void)
> > +{
> > +	/* do nothing: rely on x86_hyper_xen_hvm for the initialization */
> > +	return 0;
> > +	
> > +}
> > +EXPORT_SYMBOL(xen_guest_init);
> 
> _GPL please.

OK

> 
> >  #endif
> > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> > index 3ae96a9..52a98ff 100644
> > --- a/drivers/tty/hvc/hvc_xen.c
> > +++ b/drivers/tty/hvc/hvc_xen.c
> > @@ -578,6 +578,9 @@ static int xen_cons_init(void)
> >  	if (!xen_domain())
> >  		return 0;
> >  
> > +	/* retrieve xen infos  */
> > +	xen_guest_init();
> 
> So shouldn't this be:
> 	if (xen_guest_init())
> 		return .. something?

yes, I'll do that


> > +
> >  	if (xen_initial_domain())
> >  		ops = &dom0_hvc_ops;
> >  	else {
> > diff --git a/include/xen/xen.h b/include/xen/xen.h
> > index 2c0d3a5..792a4d2 100644
> > --- a/include/xen/xen.h
> > +++ b/include/xen/xen.h
> > @@ -9,8 +9,10 @@ enum xen_domain_type {
> >  
> >  #ifdef CONFIG_XEN
> >  extern enum xen_domain_type xen_domain_type;
> > +int xen_guest_init(void);
> >  #else
> >  #define xen_domain_type		XEN_NATIVE
> > +static inline int xen_guest_init(void) { return 0; }
> >  #endif
> >  
> >  #define xen_domain()		(xen_domain_type != XEN_NATIVE)
> > -- 
> > 1.7.2.5
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > http://lists.xen.org/xen-devel
> 
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