virtio: assert 32 bit features in transports

At this point, no transports set any of the high 32 feature bits.
Since transports generally can't (yet) cope with such bits, add BUG_ON
checks to make sure they are not set by mistake.

Based on rproc patch by Rusty.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>

2 files changed, 6 insertions, 0 deletions

diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 2336c7e3b0cf..f5575ccdbb65 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -103,6 +103,9 @@ static void kvm_finalize_features(struct virtio_device *vdev)
         /* Give virtio_ring a chance to accept features. */
         vring_transport_features(vdev);
 
+        /* Make sure we don't have any features > 32 bits! */
+        BUG_ON((u32)vdev->features != vdev->features);
+
         memset(out_features, 0, desc->feature_len);
         bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
         for (i = 0; i < bits; i++) {
diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 56d78956a8cb..244d611a0df2 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -714,6 +714,9 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
         /* Give virtio_ring a chance to accept features. */
         vring_transport_features(vdev);
 
+        /* Make sure we don't have any features > 32 bits! */
+        BUG_ON((u32)vdev->features != vdev->features);
+
         features->index = 0;
         features->features = cpu_to_le32(vdev->features);
         /* Write the feature bits to the host. */