On Thu, 21 Mar 2013 18:59:25 +1030
Rusty Russell [off-list ref] wrote:

It seemed like a good idea, but it's actually a pain when we get more
than 32 feature bits.  Just change it to a u32 for now.

Cc: Ohad Ben-Cohen <redacted>
Cc: Brian Swetland <redacted>
Cc: Cornelia Huck <redacted>
Cc: Pawel Moll <redacted>
Cc: Christian Borntraeger <redacted>
Signed-off-by: Rusty Russell <redacted>
---
 drivers/char/virtio_console.c          |    2 +-
 drivers/lguest/lguest_device.c         |    2 +-
 drivers/remoteproc/remoteproc_virtio.c |    2 +-
 drivers/s390/kvm/kvm_virtio.c          |    2 +-
 drivers/virtio/virtio.c                |   10 +++++-----
 drivers/virtio/virtio_mmio.c           |    8 ++------
 drivers/virtio/virtio_pci.c            |    3 +--
 drivers/virtio/virtio_ring.c           |    2 +-
 include/linux/virtio.h                 |    3 +--
 include/linux/virtio_config.h          |    2 +-
 tools/virtio/linux/virtio.h            |   22 +---------------------
 tools/virtio/linux/virtio_config.h     |    2 +-
 tools/virtio/virtio_test.c             |    5 ++---
 tools/virtio/vringh_test.c             |   16 ++++++++--------
 14 files changed, 27 insertions(+), 54 deletions(-)

I didn't try this patch, but wouldn't virtio_ccw need something like
the change below as well?

--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c

@@ -440,7 +440,6 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
 {
 	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
 	struct virtio_feature_desc *features;
-	int i;
 	struct ccw1 *ccw;
 
 	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);

@@ -454,19 +453,15 @@ static void virtio_ccw_finalize_features(struct virtio_device *vdev)
 	/* Give virtio_ring a chance to accept features. */
 	vring_transport_features(vdev);
 
-	for (i = 0; i < sizeof(*vdev->features) / sizeof(features->features);
-	     i++) {
-		int highbits = i % 2 ? 32 : 0;
-		features->index = i;
-		features->features = cpu_to_le32(vdev->features[i / 2]
-						 >> highbits);
-		/* Write the feature bits to the host. */
-		ccw->cmd_code = CCW_CMD_WRITE_FEAT;
-		ccw->flags = 0;
-		ccw->count = sizeof(*features);
-		ccw->cda = (__u32)(unsigned long)features;
-		ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
-	}
+	features->index = 0;
+	features->features = cpu_to_le32(vdev->features);
+	/* Write the feature bits to the host. */
+	ccw->cmd_code = CCW_CMD_WRITE_FEAT;
+	ccw->flags = 0;
+	ccw->count = sizeof(*features);
+	ccw->cda = (__u32)(unsigned long)features;
+	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
+
 out_free:
 	kfree(features);
 	kfree(ccw);