Re: [PATCH] drivers/vfio: Fix an 8-byte alignment issue

[Joe Perches <joe@perches.com>]

On Wed, 2018-10-17 at 13:18 -0500, Wenwen Wang wrote:
> This patch adds a 4-byte reserved field in the structure
> vfio_eeh_pe_op to make sure that the u64 fields in the structure
> vfio_eeh_pe_err are 8-byte aligned.
> 
> Signed-off-by: Wenwen Wang <wang6495@umn.edu>
> ---
>  include/uapi/linux/vfio.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 1aa7b82..3e71ded 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -729,6 +729,7 @@ struct vfio_eeh_pe_op {
>  	__u32 argsz;
>  	__u32 flags;
>  	__u32 op;
> +	__u32 __res;
>  	union {
>  		struct vfio_eeh_pe_err err;
>  	};

Why use an anonymous union for a single element?
Why not make struct vfio_eeh_pe_err __aligned(8)?
Why not make the u64 structure elements of
struct ufio_eeh_pe_err __aligned_u64?