linux-kernel - Re: [Xen-devel] [PATCH v11 11/12] xen/pvh: Disable PV code that does not work with PVH.

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Date:	Wed, 18 Dec 2013 15:22:23 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
	<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>,
	<mukesh.rathor@...cle.com>, <jbeulich@...e.com>
Subject: Re: [Xen-devel] [PATCH v11 11/12] xen/pvh: Disable PV code that does
 not work with PVH.

On Wed, 18 Dec 2013, Konrad Rzeszutek Wilk wrote:
> On Wed, Dec 18, 2013 at 02:19:28PM +0000, Stefano Stabellini wrote:
> > On Tue, 17 Dec 2013, Konrad Rzeszutek Wilk wrote:
> > > From: Mukesh Rathor <mukesh.rathor@...cle.com>
> > > 
> > > As we do not have yet a mechanism for that.
> > > 
> > > Signed-off-by: Mukesh Rathor <mukesh.rathor@...cle.com>
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > 
> > Even though we don't even compile cpu_hotplug on ARM yet, I don't like
> > this change because it affects ARM guests too.
> 
> Perhaps then just #ifdef it with CONFIG_X86 for right now?

That or a comment.


> > Please add a note about ARM guests in the FIXME line.
> 
> Good idea. Is the offline/online part working in ARM? Or is that it
> has not been tested?

At the moment we are using PSCI only on ARM (that is a firmware
interface that we are "emulating" in the hypervisor), but it is not
exactly the same: PSCI is about enabling secondary cpus or
disabling/suspending cpus. It is not about cpu-hotplug. So one day we
might want both.



> > >  drivers/xen/cpu_hotplug.c | 4 +++-
> > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> > > index cc6513a..cbb02af 100644
> > > --- a/drivers/xen/cpu_hotplug.c
> > > +++ b/drivers/xen/cpu_hotplug.c
> > > @@ -4,6 +4,7 @@
> > >  
> > >  #include <xen/xen.h>
> > >  #include <xen/xenbus.h>
> > > +#include <xen/features.h>
> > >  
> > >  #include <asm/xen/hypervisor.h>
> > >  #include <asm/cpu.h>
> > > @@ -102,7 +103,8 @@ static int __init setup_vcpu_hotplug_event(void)
> > >  	static struct notifier_block xsn_cpu = {
> > >  		.notifier_call = setup_cpu_watcher };
> > >  
> > > -	if (!xen_pv_domain())
> > > +	/* PVH TBD/FIXME: future work */
> > > +	if (!xen_pv_domain() || xen_feature(XENFEAT_auto_translated_physmap))
> > >  		return -ENODEV;
> > >  
> > >  	register_xenstore_notifier(&xsn_cpu);
> > 
> 
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