Re: [PATCH v2 1/1] s390x: css: report errors from ccw_dstream_read/write

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 9 Apr 2021 10:38:37 +0200
Halil Pasic <pasic@linux.ibm.com> wrote:

> On Thu,  8 Apr 2021 18:32:09 +0200
> Pierre Morel <pmorel@linux.ibm.com> wrote:
> 
> > ccw_dstream_read/write functions returned values are sometime
> > not taking into account and reported back to the upper level
> > of interpretation of CCW instructions.
> > 
> > It follows that accessing an invalid address does not trigger
> > a subchannel status program check to the guest as it should.
> > 
> > Let's test the return values of ccw_dstream_write[_buf] and
> > ccw_dstream_read[_buf] and report it to the caller.
> > 
> > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>  
> 
> Acked-by: Halil Pasic <pasic@linux.ibm.com>
> 
> I did not look into the whole scsw.count stuff or into wether
> your changes to 3270 (look form <mark></mark> in the diff part) affect
> more than just ccw_dstream_*.
> 
> I would have preferred this patch split up based on the intended effect
> and thus also subsystem (css, virtio-ccw, 3270), but I've alluded to
> that before, and since we are in a hurry I can live with it as is.
> 
> Regards,
> Halil
> 
> > ---
> >  hw/char/terminal3270.c | 11 +++++--
> >  hw/s390x/3270-ccw.c    |  5 +++-
> >  hw/s390x/css.c         | 14 +++++----
> >  hw/s390x/virtio-ccw.c  | 66 ++++++++++++++++++++++++++++++------------
> >  4 files changed, 69 insertions(+), 27 deletions(-)
> > 
> > diff --git a/hw/char/terminal3270.c b/hw/char/terminal3270.c
> > index a9a46c8ed3..82e85fac2e 100644
> > --- a/hw/char/terminal3270.c
> > +++ b/hw/char/terminal3270.c
> > @@ -200,9 +200,13 @@ static int read_payload_3270(EmulatedCcw3270Device *dev)
> >  {
> >      Terminal3270 *t = TERMINAL_3270(dev);
> >      int len;
> > +    int ret;
> >  
> >      len = MIN(ccw_dstream_avail(get_cds(t)), t->in_len);
> > -    ccw_dstream_write_buf(get_cds(t), t->inv, len);
> > +    ret = ccw_dstream_write_buf(get_cds(t), t->inv, len);
> > +    if (ret < 0) {
> > +        return ret;
> > +    }
> >      t->in_len -= len;
> >  
> >      return len;
> > @@ -260,7 +264,10 @@ static int write_payload_3270(EmulatedCcw3270Device *dev, uint8_t cmd)
> >  
> >      t->outv[out_len++] = cmd;
> >      do {
> > -        ccw_dstream_read_buf(get_cds(t), &t->outv[out_len], len);
> > +        retval = ccw_dstream_read_buf(get_cds(t), &t->outv[out_len], len);
> > +        if (retval < 0) {
> > +            return retval;
> > +        }
> >          count = ccw_dstream_avail(get_cds(t));
> >          out_len += len;
> >  
> > diff --git a/hw/s390x/3270-ccw.c b/hw/s390x/3270-ccw.c
> > index 821319eee6..f3e7342b1e 100644
> > --- a/hw/s390x/3270-ccw.c
> > +++ b/hw/s390x/3270-ccw.c
> > @@ -31,6 +31,9 @@ static int handle_payload_3270_read(EmulatedCcw3270Device *dev, CCW1 *ccw)
> >      }
> >  
> >      len = ck->read_payload_3270(dev);  
> 
> <mark>
> 
> > +    if (len < 0) {
> > +        return len;
> > +    }
> >      ccw_dev->sch->curr_status.scsw.count = ccw->count - len;
> >    
> 
> </mark>
> 
> Do we eventually update scsw.count?

I think we can consider the contents of scsw.count 'unpredictable', no?

> 
> >      return 0;
> > @@ -50,7 +53,7 @@ static int handle_payload_3270_write(EmulatedCcw3270Device *dev, CCW1 *ccw)
> >      len = ck->write_payload_3270(dev, ccw->cmd_code);
> >  
> >      if (len <= 0) {  
> 
> <mark>
> > -        return -EIO;
> > +        return len ? len : -EIO;  
> 
> </mark>
> 
> >      }
> >  
> >      ccw_dev->sch->curr_status.scsw.count = ccw->count - len;
> > diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> > index fe47751df4..4149b8e5a7 100644  
>