Re: [PATCH v2 1/1] s390/ipl: sync back loadparm

[Halil Pasic <pasic@linux.ibm.com>]

On Mon, 9 Mar 2020 14:44:20 +0100
David Hildenbrand <david@redhat.com> wrote:

> On 09.03.20 14:32, Halil Pasic wrote:
> > We expose loadparm as a r/w machine property, but if loadparm is set by
> > the guest via DIAG 308, we don't update the property. Having a
> > disconnect between the guest view and the QEMU property is not nice in
> > itself, but things get even worse for SCSI, where under certain
> > circumstances (see 789b5a401b "s390: Ensure IPL from SCSI works as
> > expected" for details) we call s390_gen_initial_iplb() on resets
> > effectively overwriting the guest/user supplied loadparm with the stale
> > value.
> > 
> > Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> > Fixes: 7104bae9de ("hw/s390x: provide loadparm property for the machine")
> > Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
> > Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
> > Reviewed-by: Viktor Mihajlovski <mihajlov@linux.ibm.com>
> > Tested-by: Marc Hartmayer <mhartmay@linux.ibm.com>
> > ---
> > v1 --> v2:
> > * tweaked the Fixes tag (Connie)
> > * s/mo/machine/ (David)
> > * We decided to not abort if the setter fails. It is not clear where
> >   do the validation logic come from in the first place. For now lets put
> >   out a warning if things go wrong.
> >   The warning we get looks something like:
> >   qemu-system-s390x: warning: LOADPARM: invalid character '?' (ASCII 0x3f)
> > * I keept the r-b's and the tested-by as the changes are minor. Please
> >   shout at me if you object.
> > ---
> >  hw/s390x/ipl.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> > index 9c1ecd423c..8bd50de44c 100644
> > --- a/hw/s390x/ipl.c
> > +++ b/hw/s390x/ipl.c
> > @@ -538,6 +538,30 @@ static bool is_virtio_scsi_device(IplParameterBlock *iplb)
> >      return is_virtio_ccw_device_of_type(iplb, VIRTIO_ID_SCSI);
> >  }
> >  
> > +static void update_machine_ipl_properties(IplParameterBlock *iplb)
> > +{
> > +    Object *machine = qdev_get_machine();
> > +    Error *err = NULL;
> > +
> > +    /* Sync loadparm */
> > +    if (iplb->flags & DIAG308_FLAGS_LP_VALID) {
> > +        char ascii_loadparm[8];
> > +        int i;
> > +        uint8_t *ebcdic_loadparm = iplb->loadparm;
> 
> Nit: move this to the top

Do you mean (reverse xmass tree)

+    if (iplb->flags & DIAG308_FLAGS_LP_VALID) {
+        uint8_t *ebcdic_loadparm = iplb->loadparm;
+        char ascii_loadparm[8];
+        int i;

or do you mean I should make the declarations function scope
instead of block scope? 

Regards,
Halil

> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
>