On Mon, 8 Dec 2014 15:06:03 +0200 "Michael S. Tsirkin" <[email protected]> wrote:
> What does it mean if rev 1 device does not set > VIRTIO_F_VERSION_1? E.g. is it native endian? My understanding is that revision only determines the set of channel commands supported by the device, and their payload. IOW, it just governs the transport-specific way to communicate; things like endianness are independent of that and only governed by the VERSION_1 bit which has rev 1 as a pre-req. > > Let's not even try to drive such devices: > fail attempts to finalize features. > virtio core will detect this and bail out. Of course, we can still make the decision to refuse non-VERSION_1 devices if rev 1 has been negotiated, but I'm still not quite sure what this buys us. > > Signed-off-by: Michael S. Tsirkin <[email protected]> > --- > drivers/s390/kvm/virtio_ccw.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > 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; > > + if (vcdev->revision == 1 && If we decide to keep this check, it should be for rev >= 1, though. > + !__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. Unless someone else has a good argument in favour of this change. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
