Re: [PATCH RFC v2 02/12] vfio: linux-headers update for vfio-ccw

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 18 Jan 2017 13:41:47 +0100
Cornelia Huck <cornelia.huck@de.ibm.com> wrote:

> On Wed, 18 Jan 2017 10:51:17 +0800
> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> 
> > * Alex Williamson <alex.williamson@redhat.com> [2017-01-17 14:51:42 -0700]:
> >   
> > > On Thu, 12 Jan 2017 08:25:03 +0100
> > > Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> > >   
> > > > From: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > > 
> > > > This is a placeholder for a linux-headers update.
> > > > 
> > > > Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > > ---
> > > >  include/standard-headers/asm-s390/vfio_ccw.h | 28 ++++++++++++++++++++++++++++
> > > >  linux-headers/linux/vfio.h                   | 17 +++++++++++++++++
> > > >  2 files changed, 45 insertions(+)
> > > >  create mode 100644 include/standard-headers/asm-s390/vfio_ccw.h
> > > > 
> > > > diff --git a/include/standard-headers/asm-s390/vfio_ccw.h b/include/standard-headers/asm-s390/vfio_ccw.h
> > > > new file mode 100644
> > > > index 0000000..cddc09b
> > > > --- /dev/null
> > > > +++ b/include/standard-headers/asm-s390/vfio_ccw.h
> > > > @@ -0,0 +1,28 @@
> > > > +/*
> > > > + * Interfaces for vfio-ccw
> > > > + *
> > > > + * Copyright IBM Corp. 2017
> > > > + *
> > > > + * This program is free software; you can redistribute it and/or modify
> > > > + * it under the terms of the GNU General Public License (version 2 only)
> > > > + * as published by the Free Software Foundation.
> > > > + *
> > > > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > > > + */
> > > > +
> > > > +#ifndef _VFIO_CCW_H_
> > > > +#define _VFIO_CCW_H_
> > > > +
> > > > +#include "standard-headers/linux/types.h"
> > > > +
> > > > +struct ccw_io_region {
> > > > +#define ORB_AREA_SIZE 12
> > > > +	uint8_t  orb_area[ORB_AREA_SIZE];
> > > > +#define SCSW_AREA_SIZE 12
> > > > +	uint8_t  scsw_area[SCSW_AREA_SIZE];
> > > > +#define IRB_AREA_SIZE 96
> > > > +	uint8_t  irb_area[IRB_AREA_SIZE];
> > > > +	uint32_t ret_code;
> > > > +} QEMU_PACKED;
> > > > +
> > > > +#endif  
> > > 
> > > This is really part of the uapi for the vfio-ccw mdev device, isn't it?  
> > Yes, it is.
> >   
> > > Should it really be buried in asm-s390 in the kernel?
> > >   
> > We had an internal discussion on this question before, since we think
> > this interface is strongly s390 dependent, we put it here. What do you
> > suggest? Thanks,  
> 
> As there are already architecture-specific definitions in the common
> file, having everything in the same file is probably better. I'm
> certainly not against moving it out from asm-s390.

As soon as we use it for the interface definition to the vfio region, I
think it makes sense for it to move to uapi.  It's not really
architecture specific as much as it is device specific, for a device
which happens to only appear on s390 hardware.  Putting it in uapi
should also make sure people think twice about changing it.  Thanks,

Alex