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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: linux-kernel@vger.kernel.org, dahi@linux.vnet.ibm.com,
	rusty@rustcorp.com.au,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	linux390@de.ibm.com, Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux-s390@vger.kernel.org
Subject: Re: [PATCH v3 4/6] virtio_ccw: rev 1 devices set VIRTIO_F_VERSION_1
Date: Tue, 9 Dec 2014 20:55:16 +0200	[thread overview]
Message-ID: <20141209185516.GB19260@redhat.com> (raw)
In-Reply-To: <20141209182319.20ce2dec.cornelia.huck@de.ibm.com>

On Tue, Dec 09, 2014 at 06:23:19PM +0100, Cornelia Huck wrote:
> On Tue, 9 Dec 2014 14:21:18 +0200
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Tue, Dec 09, 2014 at 12:01:23PM +0100, Cornelia Huck wrote:
> > > On Mon, 8 Dec 2014 15:06:03 +0200
> > > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > > > diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> > > > index 789275f..f9f87ba 100644
> > > > --- a/drivers/s390/kvm/virtio_ccw.c
> > > > +++ b/drivers/s390/kvm/virtio_ccw.c
> > > > @@ -758,6 +758,13 @@ static int virtio_ccw_finalize_features(struct virtio_device *vdev)
> > > >  	struct virtio_feature_desc *features;
> > > >  	struct ccw1 *ccw;
> 
> This needs
> 
> +	struct virtio_device *vdev = &vcdev->vdev;
> 
> to make it compile :)
> 
> > > > 
> > > > +	if (vcdev->revision == 1 &&
> > > 
> > > If we decide to keep this check, it should be for rev >= 1, though.
> > 
> > Fine, though this is theoretical, right?
> > Ican change this with a patch on top.
> > 
> > > > +	    !__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
> > > > +		dev_err(&vdev->dev, "virtio: device uses revision 1 "
> > > > +			"but does not have VIRTIO_F_VERSION_1\n");
> > > > +		return -EINVAL;
> > > > +	}
> > > > +
> > > >  	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
> > > >  	if (!ccw)
> > > >  		return 0;
> > > 
> > > I'm still not convinced by this change: I'd prefer to allow rev 1
> > > without VERSION_1, especially as the core makes all its decisions based
> > > upon VERSION_1.
> > 
> > At the moment, but this is an implementation detail.
> > This is exactly why I want this hard requirement in code.
> > 
> > 
> > > Unless someone else has a good argument in favour of
> > > this change.
> > 
> > 
> > Let's not commit to something we are not sure we
> > can support.
> > 
> > We can always remove this code, but once we release
> > guest we won't be able to drop it.
> > 
> 
> OK, with your qemu patch on the host side this seems to be fine. No
> further objections from me for now.


I fixed up my tree and pushed, so it should be good for testing now.

-- 
MST

  reply	other threads:[~2014-12-09 18:55 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-08 13:05 [PATCH v3 0/6] virtio 1.0 enhancements Michael S. Tsirkin
2014-12-08 13:05 ` [PATCH v3 1/6] virtio: add API to detect legacy devices Michael S. Tsirkin
2014-12-08 13:05 ` [PATCH v3 2/6] virtio_ccw: legacy: don't negotiate rev 1/features Michael S. Tsirkin
2014-12-09 10:35   ` Cornelia Huck
2014-12-08 13:05 ` [PATCH v3 3/6] virtio: allow finalize_features to fail Michael S. Tsirkin
2014-12-09 10:46   ` Cornelia Huck
2014-12-09 12:07     ` Michael S. Tsirkin
2014-12-09 12:56       ` Cornelia Huck
2014-12-08 13:06 ` [PATCH v3 4/6] virtio_ccw: rev 1 devices set VIRTIO_F_VERSION_1 Michael S. Tsirkin
2014-12-09 11:01   ` Cornelia Huck
2014-12-09 12:21     ` Michael S. Tsirkin
2014-12-09 17:23       ` Cornelia Huck
2014-12-09 18:55         ` Michael S. Tsirkin [this message]
2014-12-09 19:40         ` Michael S. Tsirkin
2014-12-10  8:41           ` Cornelia Huck
2014-12-08 13:06 ` [PATCH v3 5/6] virtio_balloon: drop legacy_only driver flag Michael S. Tsirkin
2014-12-09 11:24   ` Cornelia Huck
2014-12-08 13:06 ` [PATCH v3 6/6] virtio: " Michael S. Tsirkin
2014-12-09 11:24   ` Cornelia Huck

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