Re: [PATCH v5 15/15] vdpa: Add x-svq to NetdevVhostVDPAOptions

[Eugenio Perez Martin <eperezma@redhat.com>]

On Tue, Mar 8, 2022 at 9:02 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Mar 08, 2022 at 08:32:07AM +0100, Eugenio Perez Martin wrote:
> > On Tue, Mar 8, 2022 at 8:11 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> > >
> > > On Mon, Mar 07, 2022 at 04:33:34PM +0100, Eugenio Pérez wrote:
> > > > Finally offering the possibility to enable SVQ from the command line.
> > > >
> > > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > > ---
> > > >  qapi/net.json    |  8 +++++++-
> > > >  net/vhost-vdpa.c | 48 ++++++++++++++++++++++++++++++++++++++++--------
> > > >  2 files changed, 47 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/qapi/net.json b/qapi/net.json
> > > > index 7fab2e7cd8..d626fa441c 100644
> > > > --- a/qapi/net.json
> > > > +++ b/qapi/net.json
> > > > @@ -445,12 +445,18 @@
> > > >  # @queues: number of queues to be created for multiqueue vhost-vdpa
> > > >  #          (default: 1)
> > > >  #
> > > > +# @svq: Start device with (experimental) shadow virtqueue. (Since 7.0)
> > > > +#
> > > > +# Features:
> > > > +# @unstable: Member @svq is experimental.
> > > > +#
> > > >  # Since: 5.1
> > > >  ##
> > > >  { 'struct': 'NetdevVhostVDPAOptions',
> > > >    'data': {
> > > >      '*vhostdev':     'str',
> > > > -    '*queues':       'int' } }
> > > > +    '*queues':       'int',
> > > > +    '*svq':          {'type': 'bool', 'features' : [ 'unstable'] } } }
> > > >
> > > >  ##
> > > >  # @NetClientDriver:
> > >
> > > I think this should be x-svq same as other unstable features.
> > >
> >
> > I'm fine with both, but I was pointed to the other direction at [1] and [2].
> >
> > Thanks!
> >
> > [1] https://patchwork.kernel.org/project/qemu-devel/patch/20220302203012.3476835-15-eperezma@redhat.com/
> > [2] https://lore.kernel.org/qemu-devel/20220303185147.3605350-15-eperezma@redhat.com/
>
>
> I think what Markus didn't know is that a bunch of changes in
> behaviour will occur before we rename it to "svq".
> The rename is thus less of a bother more of a bonus.
>

I'm totally fine with going back to x-svq. I'm not sure if it's more
appropriate to do different modes of different parameters (svq=off,
dynamic-svq=on) or different modes of the same parameter (svq=on vs
svq=on_migration). Or something totally different.

My impression is that all of the changes are covered with @unstable
but I can see the advantage of x- prefix since we have not come to an
agreement on it. I think it's the first time it is mentioned in the
mail list.

Do you want me to send a new series with x- prefix?

Thanks!

> > > > diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> > > > index 1e9fe47c03..c827921654 100644
> > > > --- a/net/vhost-vdpa.c
> > > > +++ b/net/vhost-vdpa.c
> > > > @@ -127,7 +127,11 @@ err_init:
> > > >  static void vhost_vdpa_cleanup(NetClientState *nc)
> > > >  {
> > > >      VhostVDPAState *s = DO_UPCAST(VhostVDPAState, nc, nc);
> > > > +    struct vhost_dev *dev = s->vhost_vdpa.dev;
> > > >
> > > > +    if (dev && dev->vq_index + dev->nvqs == dev->vq_index_end) {
> > > > +        g_clear_pointer(&s->vhost_vdpa.iova_tree, vhost_iova_tree_delete);
> > > > +    }
> > > >      if (s->vhost_net) {
> > > >          vhost_net_cleanup(s->vhost_net);
> > > >          g_free(s->vhost_net);
> > > > @@ -187,13 +191,23 @@ static NetClientInfo net_vhost_vdpa_info = {
> > > >          .check_peer_type = vhost_vdpa_check_peer_type,
> > > >  };
> > > >
> > > > +static int vhost_vdpa_get_iova_range(int fd,
> > > > +                                     struct vhost_vdpa_iova_range *iova_range)
> > > > +{
> > > > +    int ret = ioctl(fd, VHOST_VDPA_GET_IOVA_RANGE, iova_range);
> > > > +
> > > > +    return ret < 0 ? -errno : 0;
> > > > +}
> > > > +
> > > >  static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
> > > > -                                           const char *device,
> > > > -                                           const char *name,
> > > > -                                           int vdpa_device_fd,
> > > > -                                           int queue_pair_index,
> > > > -                                           int nvqs,
> > > > -                                           bool is_datapath)
> > > > +                                       const char *device,
> > > > +                                       const char *name,
> > > > +                                       int vdpa_device_fd,
> > > > +                                       int queue_pair_index,
> > > > +                                       int nvqs,
> > > > +                                       bool is_datapath,
> > > > +                                       bool svq,
> > > > +                                       VhostIOVATree *iova_tree)
> > > >  {
> > > >      NetClientState *nc = NULL;
> > > >      VhostVDPAState *s;
> > > > @@ -211,6 +225,8 @@ static NetClientState *net_vhost_vdpa_init(NetClientState *peer,
> > > >
> > > >      s->vhost_vdpa.device_fd = vdpa_device_fd;
> > > >      s->vhost_vdpa.index = queue_pair_index;
> > > > +    s->vhost_vdpa.shadow_vqs_enabled = svq;
> > > > +    s->vhost_vdpa.iova_tree = iova_tree;
> > > >      ret = vhost_vdpa_add(nc, (void *)&s->vhost_vdpa, queue_pair_index, nvqs);
> > > >      if (ret) {
> > > >          qemu_del_net_client(nc);
> > > > @@ -266,6 +282,7 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
> > > >      g_autofree NetClientState **ncs = NULL;
> > > >      NetClientState *nc;
> > > >      int queue_pairs, i, has_cvq = 0;
> > > > +    g_autoptr(VhostIOVATree) iova_tree = NULL;
> > > >
> > > >      assert(netdev->type == NET_CLIENT_DRIVER_VHOST_VDPA);
> > > >      opts = &netdev->u.vhost_vdpa;
> > > > @@ -285,29 +302,44 @@ int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
> > > >          qemu_close(vdpa_device_fd);
> > > >          return queue_pairs;
> > > >      }
> > > > +    if (opts->svq) {
> > > > +        struct vhost_vdpa_iova_range iova_range;
> > > > +
> > > > +        if (has_cvq) {
> > > > +            error_setg(errp, "vdpa svq does not work with cvq");
> > > > +            goto err_svq;
> > > > +        }
> > > > +        vhost_vdpa_get_iova_range(vdpa_device_fd, &iova_range);
> > > > +        iova_tree = vhost_iova_tree_new(iova_range.first, iova_range.last);
> > > > +    }
> > > >
> > > >      ncs = g_malloc0(sizeof(*ncs) * queue_pairs);
> > > >
> > > >      for (i = 0; i < queue_pairs; i++) {
> > > >          ncs[i] = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> > > > -                                     vdpa_device_fd, i, 2, true);
> > > > +                                     vdpa_device_fd, i, 2, true, opts->svq,
> > > > +                                     iova_tree);
> > > >          if (!ncs[i])
> > > >              goto err;
> > > >      }
> > > >
> > > >      if (has_cvq) {
> > > >          nc = net_vhost_vdpa_init(peer, TYPE_VHOST_VDPA, name,
> > > > -                                 vdpa_device_fd, i, 1, false);
> > > > +                                 vdpa_device_fd, i, 1, false, opts->svq,
> > > > +                                 iova_tree);
> > > >          if (!nc)
> > > >              goto err;
> > > >      }
> > > >
> > > > +    iova_tree = NULL;
> > > >      return 0;
> > > >
> > > >  err:
> > > >      if (i) {
> > > >          qemu_del_net_client(ncs[0]);
> > > >      }
> > > > +
> > > > +err_svq:
> > > >      qemu_close(vdpa_device_fd);
> > > >
> > > >      return -1;
> > > > --
> > > > 2.27.0
> > >
>