Re: [Qemu-devel] [PATCH 7/7] vhost-user: add a new message to disable/enable a specific virt queue.

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

On Wed, Sep 09, 2015 at 09:38:12PM +0800, Yuanhan Liu wrote:
> On Wed, Sep 09, 2015 at 01:45:50PM +0300, Michael S. Tsirkin wrote:
> > On Tue, Sep 08, 2015 at 03:38:47PM +0800, Yuanhan Liu wrote:
> > > From: Changchun Ouyang <changchun.ouyang@intel.com>
> > > 
> > > Add a new message, VHOST_USER_SET_VRING_FLAG, to enable and disable
> > > a specific virt queue, which is similar to attach/detach queue for
> > > tap device.
> > > 
> > > virtio driver on guest doesn't have to use max virt queue pair, it
> > > could enable any number of virt queue ranging from 1 to max virt
> > > queue pair.
> > > 
> > > Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> > > Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> > 
> > Fine, but I would like to make this dependent on the MQ flag.
> 
> Reasonable.
> 
> > 
> > 
> > > ---
> > >  docs/specs/vhost-user.txt         | 10 ++++++++++
> > >  hw/net/vhost_net.c                | 18 ++++++++++++++++++
> > >  hw/net/virtio-net.c               |  2 ++
> > >  hw/virtio/vhost-user.c            | 32 ++++++++++++++++++++++++++++----
> > >  include/hw/virtio/vhost-backend.h |  2 ++
> > >  include/net/vhost_net.h           |  1 +
> > >  6 files changed, 61 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> > > index 99d79be..c2c38f3 100644
> > > --- a/docs/specs/vhost-user.txt
> > > +++ b/docs/specs/vhost-user.txt
> > > @@ -325,3 +325,13 @@ Message types
> > >        Query how many queues the backend supports. This request should be
> > >        sent only when VHOST_USER_PROTOCOL_F_MQ is set in quried protocol
> > >        features by VHOST_USER_GET_PROTOCOL_FEATURES.
> > > +
> > > + * VHOST_USER_SET_VRING_FLAG
> > 
> > 
> > SET_VRIHG_ENABLE would be a better name.
> 
> Okay.
> 
> > 
> > > +
> > > +      Id: 18
> > > +      Equivalent ioctl: N/A
> > > +      Master payload: vring state description
> > > +
> > > +      Set the flag(1 for enable and 0 for disable) to signal slave to enable
> > 
> > Space before ( please.
> 
> Okay.
> 
> > 
> > > +      or disable corresponding virt queue. This request should be sent only
> > > +      when the protocol feature bit VHOST_USER_PROTOCOL_F_VRING_FLAG is set.
> > > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > > index 141b557..7d9cc8d 100644
> > > --- a/hw/net/vhost_net.c
> > > +++ b/hw/net/vhost_net.c
> > > @@ -418,6 +418,19 @@ VHostNetState *get_vhost_net(NetClientState *nc)
> > >  
> > >      return vhost_net;
> > >  }
> > > +
> > > +int vhost_set_vring_flag(NetClientState *nc, int enable)
> > > +{
> > > +    if (nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
> > > +        VHostNetState *net = get_vhost_net(nc);
> > > +        const VhostOps *vhost_ops = net->dev.vhost_ops;
> > 
> > add an empty line after declaration pls.
> 
> Got it, thanks.
> 
> > 
> > > +        if (vhost_ops->vhost_backend_mq_set_vring_flag)
> > > +            return vhost_ops->vhost_backend_mq_set_vring_flag(&net->dev, enable);
> > 
> > Coding style violation:
> > 	line too long,
> 
> Yeah, 81 chars. I thougth that's kind of acceptable. But, anyway, since
> you pointed it out, I will fix it next time.
> 
> > and should use {}.
> 
> TBH, I seldom use {} for one statement, and you could see that a lot from
> this patch set. Is it a must in qemu community?

Yes it is. It's different from the kernel.

> If so, I could fix them all.
> 
> > 
> > > +    }
> > > +
> > > +    return 0;
> > > +}
> > > +
> > >  #else
> > >  struct vhost_net *vhost_net_init(VhostNetOptions *options)
> > >  {
> > > @@ -463,4 +476,9 @@ VHostNetState *get_vhost_net(NetClientState *nc)
> > >  {
> > >      return 0;
> > >  }
> > > +
> > > +int vhost_set_vring_flag(NetClientState *nc, int enable)
> > > +{
> > > +    return 0;
> > > +}
> > >  #endif
> > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > > index 8d28e45..53f93b1 100644
> > > --- a/hw/net/virtio-net.c
> > > +++ b/hw/net/virtio-net.c
> > > @@ -407,6 +407,7 @@ static int peer_attach(VirtIONet *n, int index)
> > >      }
> > >  
> > >      if (nc->peer->info->type != NET_CLIENT_OPTIONS_KIND_TAP) {
> > > +        vhost_set_vring_flag(nc->peer, 1);
> > >          return 0;
> > >      }
> > >  
> > > @@ -422,6 +423,7 @@ static int peer_detach(VirtIONet *n, int index)
> > >      }
> > >  
> > >      if (nc->peer->info->type !=  NET_CLIENT_OPTIONS_KIND_TAP) {
> > > +        vhost_set_vring_flag(nc->peer, 0);
> > >          return 0;
> > >      }
> > >
> > 
> > makes no sense to call it for !== tap only.
> > Either call this unconditionally, or just for vhost user.
> 
> Agreed. I will make it vhost-usre specific then.
> 
> > 
> >   
> > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> > > index 11e46b5..ca6f7fa 100644
> > > --- a/hw/virtio/vhost-user.c
> > > +++ b/hw/virtio/vhost-user.c
> > > @@ -25,9 +25,10 @@
> > >  
> > >  #define VHOST_MEMORY_MAX_NREGIONS    8
> > >  #define VHOST_USER_F_PROTOCOL_FEATURES 30
> > > -#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x1ULL
> > > +#define VHOST_USER_PROTOCOL_FEATURE_MASK 0xfULL
> > >  
> > > -#define VHOST_USER_PROTOCOL_F_MQ    0
> > > +#define VHOST_USER_PROTOCOL_F_MQ            0
> > > +#define VHOST_USER_PROTOCOL_F_VRING_FLAG    1
> > >  
> > >  typedef enum VhostUserRequest {
> > >      VHOST_USER_NONE = 0,
> > > @@ -48,6 +49,7 @@ typedef enum VhostUserRequest {
> > >      VHOST_USER_GET_PROTOCOL_FEATURES = 15,
> > >      VHOST_USER_SET_PROTOCOL_FEATURES = 16,
> > >      VHOST_USER_GET_QUEUE_NUM = 17,
> > > +    VHOST_USER_SET_VRING_FLAG = 18,
> > >      VHOST_USER_MAX
> > >  } VhostUserRequest;
> > >  
> > > @@ -296,6 +298,11 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
> > >          msg.addr.index += dev->vq_index;
> > >          msg.size = sizeof(m.state);
> > >          break;
> > > +    case VHOST_USER_SET_VRING_FLAG:
> > > +        msg.state.index = dev->vq_index;
> > > +        msg.state.num = *(int*)arg;
> > > +        msg.size = sizeof(msg.state);
> > > +        break;
> > >  
> > >      case VHOST_USER_GET_VRING_BASE:
> > >          memcpy(&msg.state, arg, sizeof(struct vhost_vring_state));
> > > @@ -408,6 +415,22 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
> > >      return 0;
> > >  }
> > >  
> > > +static int vhost_user_set_vring_flag(struct vhost_dev *dev, int enable)
> > > +{
> > > +    int err;
> > > +
> > > +    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> > > +
> > > +    if (!(dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_VRING_FLAG)))
> > > +        return -1;
> > > +
> > > +    err = vhost_user_call(dev, VHOST_USER_SET_VRING_FLAG, &enable);
> > > +    if (err < 0)
> > > +        return err;
> > > +
> > > +    return 0;
> > > +}
> > > +
> > >  static int vhost_user_cleanup(struct vhost_dev *dev)
> > >  {
> > >      assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> > 
> > In fact, it's a per VQ pair call the way it's coded.
> > So pls fix it, call it for all VQs.
> 
> Let me try.
> 
> > 
> > 
> > > @@ -421,5 +444,6 @@ const VhostOps user_ops = {
> > >          .backend_type = VHOST_BACKEND_TYPE_USER,
> > >          .vhost_call = vhost_user_call,
> > >          .vhost_backend_init = vhost_user_init,
> > > -        .vhost_backend_cleanup = vhost_user_cleanup
> > > -        };
> > > +        .vhost_backend_cleanup = vhost_user_cleanup,
> > > +        .vhost_backend_mq_set_vring_flag = vhost_user_set_vring_flag,
> > > +};
> > > diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
> > > index e472f29..6fc76b7 100644
> > > --- a/include/hw/virtio/vhost-backend.h
> > > +++ b/include/hw/virtio/vhost-backend.h
> > > @@ -24,12 +24,14 @@ typedef int (*vhost_call)(struct vhost_dev *dev, unsigned long int request,
> > >               void *arg);
> > >  typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
> > >  typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
> > > +typedef int (*vhost_backend_mq_set_vring_flag)(struct vhost_dev *dev, int enable);
> > >  
> > >  typedef struct VhostOps {
> > >      VhostBackendType backend_type;
> > >      vhost_call vhost_call;
> > >      vhost_backend_init vhost_backend_init;
> > >      vhost_backend_cleanup vhost_backend_cleanup;
> > > +    vhost_backend_mq_set_vring_flag vhost_backend_mq_set_vring_flag;
> > 
> > That's quite ugly: mq is a vhost net thing.
> > Why not enable each VQ?
> 
> To define it as `vhost_backend_enable_vring'?
> 
> Thanks.
> 
> 	--yliu

Sure.

> > 
> > >  } VhostOps;
> > >  
> > >  extern const VhostOps user_ops;
> > > diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> > > index 8db723e..3ec33ff 100644
> > > --- a/include/net/vhost_net.h
> > > +++ b/include/net/vhost_net.h
> > > @@ -28,4 +28,5 @@ bool vhost_net_virtqueue_pending(VHostNetState *net, int n);
> > >  void vhost_net_virtqueue_mask(VHostNetState *net, VirtIODevice *dev,
> > >                                int idx, bool mask);
> > >  VHostNetState *get_vhost_net(NetClientState *nc);
> > > +int vhost_set_vring_flag(NetClientState * nc, int enable);
> > >  #endif
> > > -- 
> > > 1.9.0