virtio_ccw: legacy: don't negotiate rev 1/features

Legacy balloon device doesn't pretend to support revision 1 or 64 bit
features.

But just in case someone implements a broken one that does, let's not
even try to drive legacy only devices using revision 1, and let's not
give them a chance to say they support VIRTIO_F_VERSION_1 by not reading
or writing high feature bits.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 4a3e6e5..c792b5f 100644 (file)
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -733,6 +733,9 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
 
        rc = le32_to_cpu(features->features);
 
+       if (vcdev->revision == 0)
+               goto out_free;
+
        /* Read second half of the feature bits from the host. */
        features->index = 1;
        ccw->cmd_code = CCW_CMD_READ_FEAT;
@@ -775,6 +778,9 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
        ccw->cda = (__u32)(unsigned long)features;
        ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
 
+       if (vcdev->revision == 0)
+               goto out_free;
+
        features->index = 1;
        features->features = cpu_to_le32(vdev->features >> 32);
        /* Write the second half of the feature bits to the host. */
@@ -1182,9 +1188,13 @@ static int virtio_ccw_online(struct ccw_device *cdev)
        vcdev->vdev.id.vendor = cdev->id.cu_type;
        vcdev->vdev.id.device = cdev->id.cu_model;
 
-       ret = virtio_ccw_set_transport_rev(vcdev);
-       if (ret)
-               goto out_free;
+       if (virtio_device_is_legacy_only(vcdev->vdev.id)) {
+               vcdev->revision = 0;
+       } else {
+               ret = virtio_ccw_set_transport_rev(vcdev);
+               if (ret)
+                       goto out_free;
+       }
 
        ret = register_virtio_device(&vcdev->vdev);
        if (ret) {