Re: [Qemu-devel] [PATCH] pc-bios/s390-ccw: struct tpi_info must be declared as aligned(4)

[Cornelia Huck <cohuck@redhat.com>]

On Tue,  8 May 2018 12:17:52 +0200
Thomas Huth <thuth@redhat.com> wrote:

> I've run into a compilation error today with the current version of GCC 8:
> 
> In file included from s390-ccw.h:49,
>                  from main.c:12:
> cio.h:128:1: error: alignment 1 of 'struct tpi_info' is less than 4 [-Werror=packed-not-aligned]
>  } __attribute__ ((packed));
>  ^
> cc1: all warnings being treated as errors
> 
> Since the struct tpi_info contains an element ("struct subchannel_id schid")
> which is marked as aligned(4), we've got to mark the struct tpi_info as
> aligned(4), too.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  pc-bios/s390-ccw/cio.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/pc-bios/s390-ccw/cio.h b/pc-bios/s390-ccw/cio.h
> index 55eaeee..1a0795f 100644
> --- a/pc-bios/s390-ccw/cio.h
> +++ b/pc-bios/s390-ccw/cio.h
> @@ -125,7 +125,7 @@ struct tpi_info {
>      __u32 reserved3  : 12;
>      __u32 int_type   : 3;
>      __u32 reserved4  : 12;
> -} __attribute__ ((packed));
> +} __attribute__ ((packed, aligned(4)));
>  
>  /* channel command word (type 1) */
>  struct ccw1 {

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Alternatively, we could also ditch this struct and the tpi function...
but I have not given up hope yet that we might someday handle channel
I/O more canonically in the bios :)