virtio/blk: Avoid taking pointer to packed struct

clang and GCC9 refuse to compile virtio/blk.c with the following message:
virtio/blk.c:161:37: error: taking address of packed member 'geometry' of class
      or structure 'virtio_blk_config' may result in an unaligned pointer value
        struct virtio_blk_geometry *geo = &conf->geometry;

Since struct virtio_blk_geometry is in a kernel header, we can't do much
about the packed attribute, but as Peter pointed out, the solution is
rather simple: just get rid of the convenience variable and use the
original struct member directly.

Reviewed-by: Jean-Philippe Brucker <>
Suggested-by: Peter Maydell <>
Signed-off-by: Andre Przywara <>
Signed-off-by: Will Deacon <>
diff --git a/virtio/blk.c b/virtio/blk.c
index 50db6f5..f267be1 100644
--- a/virtio/blk.c
+++ b/virtio/blk.c
@@ -161,7 +161,6 @@
 	struct blk_dev *bdev = dev;
 	struct virtio_blk_config *conf = &bdev->blk_config;
-	struct virtio_blk_geometry *geo = &conf->geometry;
 	bdev->features = features;
@@ -170,7 +169,8 @@
 	conf->seg_max = virtio_host_to_guest_u32(&bdev->vdev, conf->seg_max);
 	/* Geometry */
-	geo->cylinders = virtio_host_to_guest_u16(&bdev->vdev, geo->cylinders);
+	conf->geometry.cylinders = virtio_host_to_guest_u16(&bdev->vdev,
+						conf->geometry.cylinders);
 	conf->blk_size = virtio_host_to_guest_u32(&bdev->vdev, conf->blk_size);
 	conf->min_io_size = virtio_host_to_guest_u16(&bdev->vdev, conf->min_io_size);