On 03/05/2019 18:15, Andre Przywara wrote:
> 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
> [-Werror,-Waddress-of-packed-member]
> 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.
>
> Suggested-by: Peter Maydell <peter.maydell@xxxxxxxxxx>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
I just encountered this one with GCC 9.1
> ---
> virtio/blk.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/virtio/blk.c b/virtio/blk.c
> index 50db6f5f..f267be15 100644
> --- a/virtio/blk.c
> +++ b/virtio/blk.c
> @@ -161,7 +161,6 @@ static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
> {
> 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 @@ static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
> 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);
>
