Re: [Qemu-devel] [PATCH v4 2/2] vfio-ccw: support async command subregion

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 21 May 2019 16:50:47 -0400
Farhan Ali <alifm@linux.ibm.com> wrote:

> On 05/07/2019 11:47 AM, Cornelia Huck wrote:
> > A vfio-ccw device may provide an async command subregion for
> > issuing halt/clear subchannel requests. If it is present, use
> > it for sending halt/clear request to the device; if not, fall
> > back to emulation (as done today).
> > 
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >   hw/s390x/css.c              |  27 +++++++--
> >   hw/vfio/ccw.c               | 110 +++++++++++++++++++++++++++++++++++-
> >   include/hw/s390x/s390-ccw.h |   3 +
> >   3 files changed, 134 insertions(+), 6 deletions(-)

> > diff --git a/include/hw/s390x/s390-ccw.h b/include/hw/s390x/s390-ccw.h
> > index 901d805d79a3..e9c7e1db5761 100644
> > --- a/include/hw/s390x/s390-ccw.h
> > +++ b/include/hw/s390x/s390-ccw.h
> > @@ -37,4 +37,7 @@ typedef struct S390CCWDeviceClass {
> >       IOInstEnding (*handle_request) (SubchDev *sch);
> >   } S390CCWDeviceClass;
> >   
> > +int vfio_ccw_handle_clear(SubchDev *sch);
> > +int vfio_ccw_handle_halt(SubchDev *sch);
> > +  
> 
> We are not making clear and halt functions part of the 
> S390CCWDeviceClass, is there are reason for doing this?
> Currently we handle ssch through the handle_request function, it just 
> looks a little inconsistent.

I don't quite remember why I did it this way; not sure if there is a
good reason for that (that patch has been around for too long...)

We can change such internal details later on, though. (And I think your
comment has merit.)