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

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 3 Nov 2020 13:32:47 +0100
Thomas Huth <thuth@redhat.com> wrote:

> 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...

Will do, I have other things as well anyway.