Re: [Qemu-devel] [PATCH 4/4] virtio-ccw: enable virtio-1

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Sep 10, 2015 at 11:11:20AM +0200, Cornelia Huck wrote:
> On Thu, 10 Sep 2015 12:07:18 +0300
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Fri, Sep 04, 2015 at 10:54:29AM +0200, Cornelia Huck wrote:
> > > Let's enable revision 1 for virtio-ccw devices. We can always offer
> > > VERSION_1 as drivers in legacy mode won't be able to see it anyway.
> > > 
> > > We have to introduce a way to set a lower maximum revision for a device
> > > to accommodate the following cases:
> > > - compat machines (to enforce legacy only)
> > 
> > But you don't actually set this for any compat machines.
> > If you don't, this seems a bit pointless.
> 
> Huh? The first hunk of this patch does this.

Sure. Donnu how I could miss it, sorry.

> > 
> > > - virtio-blk with scsi support (version 1 + scsi is fenced by common
> > >   code, with a user-configured max revision of 0 we can allow scsi
> > >   via not offering VERSION_1)
> > 
> > For this use, for pci users need to do disable_modern=true.
> > I find it unfortunate that for ccw one needs to do max_revision=0.
> 
> I don't like the pci concept: much too coarse-grained and not very
> future proof.
> 
> > 
> > Revision numbers generally are a ccw specific concept. I'm not sure it
> > is wise to expose it to users.
> 
> What is wrong about exposing transport-specific concepts?

Nothing. Go ahead and expose as much of the low level as
makes sense.

But it would be nice if there was also a portable way for people
that just want "virtio" and don't care about the low level details
of which transport it is.

OTOH a conservative estimate of the # of people that will want
to play with this is pretty close to 0, so maybe it does not matter
much.

> > 
> > > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > > ---
> > >  hw/s390x/s390-virtio-ccw.c |  4 ++++
> > >  hw/s390x/virtio-ccw.c      | 30 ++++++++++++++++++++++++++++--
> > >  hw/s390x/virtio-ccw.h      |  6 ++++--
> > >  3 files changed, 36 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> > > index e2a26e9..fb6e45c 100644
> > > --- a/hw/s390x/s390-virtio-ccw.c
> > > +++ b/hw/s390x/s390-virtio-ccw.c
> > > @@ -287,6 +287,10 @@ static const TypeInfo ccw_machine_info = {
> > >              .driver   = TYPE_S390_SKEYS,\
> > >              .property = "migration-enabled",\
> > >              .value    = "off",\
> > > +        },{\
> > > +            .driver = TYPE_VIRTIO_CCW_DEVICE,\
> > > +            .property = "max_revision",\
> > > +            .value = 0,\
> > >          },
> > >  
> > >  static void ccw_machine_2_4_class_init(ObjectClass *oc, void *data)
> > > diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> > > index eed7b3e..fb103b7 100644
> > > --- a/hw/s390x/virtio-ccw.c
> > > +++ b/hw/s390x/virtio-ccw.c
> > > @@ -467,7 +467,13 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > >                                                  MEMTXATTRS_UNSPECIFIED,
> > >                                                  NULL);
> > >              if (features.index == 0) {
> > > -                features.features = (uint32_t)vdev->host_features;
> > > +                if (dev->revision >= 1) {
> > > +                    /* Don't offer legacy features for modern devices. */
> > > +                    features.features = (uint32_t)
> > > +                        (vdev->host_features & ~VIRTIO_LEGACY_FEATURES);
> > > +                } else {
> > > +                    features.features = (uint32_t)vdev->host_features;
> > > +                }
> > >              } else if ((features.index == 1) && (dev->revision >= 1)) {
> > >                  /*
> > >                   * Only offer feature bits beyond 31 if the guest has
> > > @@ -768,7 +774,7 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
> > >           * need to fetch it here. Nothing to do for now, though.
> > >           */
> > >          if (dev->revision >= 0 ||
> > > -            revinfo.revision > virtio_ccw_rev_max(vdev)) {
> > > +            revinfo.revision > virtio_ccw_rev_max(dev)) {
> > >              ret = -ENOSYS;
> > >              break;
> > >          }
> > > @@ -1541,6 +1547,10 @@ static void virtio_ccw_device_plugged(DeviceState *d, Error **errp)
> > >  
> > >      sch->id.cu_model = virtio_bus_get_vdev_id(&dev->bus);
> > >  
> > > +    if (dev->max_rev >= 1) {
> > > +        virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> > > +    }
> > > +
> > >      css_generate_sch_crws(sch->cssid, sch->ssid, sch->schid,
> > >                            d->hotplugged, 1);
> > >  }
> > > @@ -1557,6 +1567,8 @@ static Property virtio_ccw_net_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1584,6 +1596,8 @@ static Property virtio_ccw_blk_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1611,6 +1625,8 @@ static Property virtio_ccw_serial_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1638,6 +1654,8 @@ static Property virtio_ccw_balloon_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1665,6 +1683,8 @@ static Property virtio_ccw_scsi_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1691,6 +1711,8 @@ static const TypeInfo virtio_ccw_scsi = {
> > >  #ifdef CONFIG_VHOST_SCSI
> > >  static Property vhost_ccw_scsi_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1729,6 +1751,8 @@ static Property virtio_ccw_rng_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >                      VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > @@ -1882,6 +1906,8 @@ static Property virtio_ccw_9p_properties[] = {
> > >      DEFINE_PROP_STRING("devno", VirtioCcwDevice, bus_id),
> > >      DEFINE_PROP_BIT("ioeventfd", VirtioCcwDevice, flags,
> > >              VIRTIO_CCW_FLAG_USE_IOEVENTFD_BIT, true),
> > > +    DEFINE_PROP_UINT32("max_revision", VirtioCcwDevice, max_rev,
> > > +                       VIRTIO_CCW_MAX_REV),
> > >      DEFINE_PROP_END_OF_LIST(),
> > >  };
> > >  
> > > diff --git a/hw/s390x/virtio-ccw.h b/hw/s390x/virtio-ccw.h
> > > index 692ddd7..7ab8367 100644
> > > --- a/hw/s390x/virtio-ccw.h
> > > +++ b/hw/s390x/virtio-ccw.h
> > > @@ -88,6 +88,7 @@ struct VirtioCcwDevice {
> > >      SubchDev *sch;
> > >      char *bus_id;
> > >      int revision;
> > > +    uint32_t max_rev;
> > >      VirtioBusState bus;
> > >      bool ioeventfd_started;
> > >      bool ioeventfd_disabled;
> > > @@ -102,9 +103,10 @@ struct VirtioCcwDevice {
> > >  };
> > >  
> > >  /* The maximum virtio revision we support. */
> > > -static inline int virtio_ccw_rev_max(VirtIODevice *vdev)
> > > +#define VIRTIO_CCW_MAX_REV 1
> > > +static inline int virtio_ccw_rev_max(VirtioCcwDevice *dev)
> > >  {
> > > -    return 0;
> > > +    return dev->max_rev;
> > >  }
> > >  
> > >  /* virtual css bus type */
> > > -- 
> > > 2.3.8
> >