From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cornelia Huck <cornelia.huck@de.ibm.com>
Subject: Re: [PATCH 1/4] s390/kvm: Handle hosts not supporting s390-virtio.
Date: Fri, 10 Aug 2012 09:45:00 +0200
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Cc: KVM <kvm@vger.kernel.org>, linux-s390 <linux-s390@vger.kernel.org>,
	qemu-devel <qemu-devel@nongnu.org>, Avi Kivity <avi@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Anthony Liguori <aliguori@us.ibm.com>,
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To: Alexander Graf <agraf@suse.de>
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On Fri, 10 Aug 2012 01:09:15 +0200
Alexander Graf <agraf@suse.de> wrote:

> 
> On 07.08.2012, at 16:52, 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.
> > 
> > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > ---
> > drivers/s390/kvm/kvm_virtio.c | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> > 
> > diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
> > index 47cccd5..408447c 100644
> > --- a/drivers/s390/kvm/kvm_virtio.c
> > +++ b/drivers/s390/kvm/kvm_virtio.c
> > @@ -418,6 +418,21 @@ static void kvm_extint_handler(struct ext_code ext_code,
> > 	}
> > }
> > 
> > +static int __init test_devices_support(void)
> 
> Today we know what this function does, but the next person running into it has no clue. Maybe add a nice description here that you're trying to access memory above ram? (is this even what you're doing here? my s390 asm is slightly rusty) :)

Good point, will add a comment.