Re: [Qemu-devel] [PATCH v4 3/5] s390x: Add I/O adapter registration.

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Wed, 09 Apr 2014 16:30:33 +0200
Alexander Graf <agraf@suse.de> wrote:

> 
> On 09.04.14 16:24, Cornelia Huck wrote:
> > On Wed, 09 Apr 2014 16:05:00 +0200
> > Alexander Graf <agraf@suse.de> wrote:
> >
> >> On 09.04.14 13:34, Cornelia Huck wrote:
> >>> Register an I/O adapter interrupt source for when virtio-ccw devices start
> >>> using adapter interrupts.
> >>>
> >>> Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
> >>> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> >>> ---
> >>>    hw/intc/s390_flic.c   |   59 +++++++++++++++++++++++++++++++++++++++++++++++++
> >>>    hw/s390x/css.c        |   51 ++++++++++++++++++++++++++++++++++++++++++
> >>>    hw/s390x/css.h        |    4 ++++
> >>>    hw/s390x/virtio-ccw.c |    4 ++++
> >>>    hw/s390x/virtio-ccw.h |    1 +
> >>>    target-s390x/cpu.h    |   33 +++++++++++++++++++++++++++
> >>>    6 files changed, 152 insertions(+)
> >>>
> >>> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> >>> index 2bf0af8..1193682 100644
> >>> --- a/hw/s390x/virtio-ccw.c
> >>> +++ b/hw/s390x/virtio-ccw.c
> >>> @@ -522,6 +522,10 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> >>>                    dev->thinint_isc = thinint->isc;
> >>>                    dev->ind_bit = thinint->ind_bit;
> >>>                    cpu_physical_memory_unmap(thinint, hw_len, 0, hw_len);
> >>> +                ret = css_register_io_adapter(CSS_IO_ADAPTER_VIRTIO,
> >>> +                                              dev->thinint_isc, true, false,
> >>> +                                              &dev->adapter_id);
> >> In all other machines the machine file is the one creating the link
> >> between a device and the interrupt controller. Can we do something
> >> similar for s390?
> > Hm. This would imply we'd need to add a virtio I/O adapter for each isc
> > (0-7) at startup, regardless whether the guest enables adapter
> > interrupts on any of those iscs. Moreover, we'd need to do the same for
> > each type (on each isc) if we add more types of I/O adapters later
> > (should we want to support one of the other adapter-interrupt using
> > devices). I'd prefer to add an I/O adapter only when needed.
> 
> I'm not sure I can follow you here. Instead of registering the interrupt 
> vector on the fly, you would still register it on the fly, but after the 
> virtio-ccw device got created, no?

You mean register-at-device-creation instead of
register-while-interpreting-ccw? We'd end up with the same problem: We
don't know which isc the guest wants to use for adapter interrupts at
that point in time, so we would need to register for all iscs. I don't
think that is what we want.