Re: [PATCH] s390-bios: Skip writing iplb location to low core for ccw ipl

[Thomas Huth <thuth@redhat.com>]

On 30/10/2020 13.28, Christian Borntraeger wrote:
> From: "Jason J. Herne" <jjherne@linux.ibm.com>
> 
> The architecture states that the iplb location is only written to low
> core for list directed ipl and not for traditional ccw ipl. If we don't
> skip this then operating systems that load by reading into low core
> memory may fail to start.

Just double-checking: But doing write_subsystem_identification()
unconditionally is ok, right?

> We should also not write the iplb pointer for network boot as it might
> overwrite content that we got via network.

FWIW, write_iplb_location() is already just a dummy function in netmain.c,
so this should not have been an issue in the network bootloader, I hope.

> Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
> Fixes: 9bfc04f9ef68 ("pc-bios: s390x: Save iplb location in lowcore")
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  pc-bios/s390-ccw/main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
> index 43c792cf9509..fc4bfaa45529 100644
> --- a/pc-bios/s390-ccw/main.c
> +++ b/pc-bios/s390-ccw/main.c
> @@ -43,7 +43,9 @@ void write_subsystem_identification(void)
>  
>  void write_iplb_location(void)
>  {
> -    lowcore->ptr_iplb = ptr2u32(&iplb);
> +    if (cutype == CU_TYPE_VIRTIO && virtio_get_device_type() != VIRTIO_ID_NET) {
> +        lowcore->ptr_iplb = ptr2u32(&iplb);
> +    }
>  }

Acked-by: Thomas Huth <thuth@redhat.com>

Christian, Cornelia, could you please pick up the patch? I'm not sure
whether I can do another PR this week for the RC...