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Date: Thu, 9 Aug 2012 12:41:57 +0200
From: Cornelia Huck <cornelia.huck@de.ibm.com>
Message-ID: <20120809124157.582fd609@BR9GNB5Z>
In-Reply-To: <50238B0D.2060604@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/4] s390/kvm: Handle hosts not supporting
	s390-virtio.
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To: Avi Kivity <avi@redhat.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>, Anthony Liguori <aliguori@us.ibm.com>, Rusty Russell <rusty@rustcorp.com.au>, KVM <kvm@vger.kernel.org>, Carsten Otte <cotte@de.ibm.com>, Sebastian Ott <sebott@linux.vnet.ibm.com>, Marcelo Tosatti <mtosatti@redhat.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, qemu-devel <qemu-devel@nongnu.org>, Alexander Graf <agraf@suse.de>, Christian Borntraeger <borntraeger@de.ibm.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>

On Thu, 09 Aug 2012 13:03:57 +0300
Avi Kivity <avi@redhat.com> wrote:

> On 08/07/2012 05:52 PM, Cornelia Huck wrote:
> > Running under a kvm host does not necessarily imply the presence of
> > a page mapped above the main memory with the virtio information;
> > however, the code includes a hard coded access to that page.
> > 
> > Instead, check for the presence of the page and exit gracefully
> > before we hit an addressing exception if it does not exist.
> > 
> >  /*
> >   * Init function for virtio
> >   * devices are in a single page above top of "normal" mem
> > @@ -443,6 +458,12 @@ static int __init kvm_devices_init(void)
> >  	}
> >  
> >  	kvm_devices = (void *) real_memory_size;
> > +	if (test_devices_support() < 0) {
> > +		vmem_remove_mapping(real_memory_size, PAGE_SIZE);
> > +		root_device_unregister(kvm_root);
> > +		/* No error. */
> > +		return 0;
> > +	}
> >  
> 
> Cleaner to defer root_device_register() until after the mapping has been
> verified.

OK, will reorder.