Re: [Qemu-devel] [PATCH v6 2/2] vhost-user: new protocol feature for multi queue

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

On Wed, Aug 12, 2015 at 02:25:42PM +0800, Ouyang Changchun wrote:
> This patch is based on top of "vhost-user: protocol updates" series
> proposed earlier by Michael S. Tsirkin.
> 
> Use new message VHOST_USER_SET_VRING_FLAG to enable and disable an
> actual 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.
> 
> It requires that VHOST_USER_F_PROTOCOL_FEATURES is present.
> 
> Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
> ---
> This is added since v5
> 
>  docs/specs/vhost-user.txt         | 17 +++++++++++++++++
>  hw/net/vhost_net.c                | 18 ++++++++++++++++++
>  hw/net/virtio-net.c               |  2 ++
>  hw/virtio/vhost-user.c            | 35 +++++++++++++++++++++++++++++++++--
>  include/hw/virtio/vhost-backend.h |  2 ++
>  include/net/vhost_net.h           |  1 +
>  6 files changed, 73 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 9390f89..cca3e5b 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -135,6 +135,10 @@ As older slaves don't support negotiating protocol features,
>  a feature bit was dedicated for this purpose:
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
>  
> +The Slave uses vring flag to notify the vhost-user whether one virtq is enabled
> +or not. This request doesn't require replies:
> +#define VHOST_USER_PROTOCOL_F_VRING_FLAG 2
> +
>  Multi queue support
>  -------------------
>  The protocol supports multiple queues by setting all index fields in the sent
> @@ -306,3 +310,16 @@ Message types
>        Bits (0-7) of the payload contain the vring index. Bit 8 is the
>        invalid FD flag. This flag is set when there is no file descriptor
>        in the ancillary data.
> +
> + * VHOST_USER_SET_VRING_FLAG
> +
> +      Id: 18
> +      Equivalent ioctl: N/A
> +      Master payload: vring state description
> +
> +      Set the flag(enable or disable) in the vring, the vhost user backend
> +      enable or disable the vring according to state.num. Olny legal if feature
> +      bit VHOST_USER_F_PROTOCOL_FEATURES is present in VHOST_USER_GET_FEATURE
> +      and feature bit VHOST_USER_PROTOCOL_F_VRING_FLAG is present in
> +      VHOST_USER_GET_PROTOCOL_FEATURES. The vring is enabled when state.num is
> +      1, otherwise, the vring is disabled.
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 9cd6c05..5fa341c 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -405,6 +405,19 @@ VHostNetState *get_vhost_net(NetClientState *nc)
>  
>      return vhost_net;
>  }
> +
> +int vhost_set_vring_flag(NetClientState *nc, unsigned int enable)
> +{
> +    if (nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
> +        struct vhost_net *net = get_vhost_net(nc);
> +        const VhostOps *vhost_ops = net->dev.vhost_ops;
> +        if (vhost_ops->vhost_backend_mq_set_vring_flag)
> +            return vhost_ops->vhost_backend_mq_set_vring_flag(&net->dev, enable);
> +    }
> +
> +    return 0;
> +}
> +
>  #else
>  struct vhost_net *vhost_net_init(VhostNetOptions *options)
>  {
> @@ -455,4 +468,9 @@ VHostNetState *get_vhost_net(NetClientState *nc)
>  {
>      return 0;
>  }
> +
> +int vhost_set_vring_flag(NetClientState *nc, unsigned int enable)
> +{
> +    return 0;
> +}
>  #endif
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 3af6faf..272b77d 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -396,6 +396,7 @@ 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;
>      }
>  
> @@ -411,6 +412,7 @@ 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;
>      }
>  
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index fb11d4c..d806ce2 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -25,7 +25,8 @@
>  
>  #define VHOST_MEMORY_MAX_NREGIONS    8
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
> -#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
> +#define VHOST_USER_PROTOCOL_F_VRING_FLAG 2
> +#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x7ULL
>  
>  typedef enum VhostUserRequest {
>      VHOST_USER_NONE = 0,
> @@ -45,6 +46,7 @@ typedef enum VhostUserRequest {
>      VHOST_USER_SET_VRING_ERR = 14,
>      VHOST_USER_GET_PROTOCOL_FEATURES = 15,
>      VHOST_USER_SET_PROTOCOL_FEATURES = 16,
> +    VHOST_USER_SET_VRING_FLAG = 18,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>  
> @@ -399,6 +401,34 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
>      return 0;
>  }
>  
> +static int vhost_user_set_vring_flag(struct vhost_dev *dev, unsigned int enable)
> +{
> +    VhostUserMsg msg = { 0 };
> +    int err;
> +
> +    assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER);
> +
> +    if ((dev->backend_features & ( 1ULL << VHOST_USER_F_PROTOCOL_FEATURES)) == 0)
> +        return -1;
> +
> +    if ((dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_VRING_FLAG)) == 0)
> +        return -1;
> +
> +    msg.request = VHOST_USER_SET_VRING_FLAG;
> +    msg.flags = VHOST_USER_VERSION;
> +    /* Set the virt queue pair index */
> +    msg.state.index = dev->vq_index / 2;

Thinking about this, this means that the index value is specific to virtio net.
This seems wrong.

> +    msg.state.num = enable;
> +    msg.size = sizeof msg.state;
> +
> +    err = vhost_user_write(dev, &msg, NULL, 0);
> +    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);
> @@ -412,5 +442,6 @@ 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..c394147 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, unsigned 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;
>  } VhostOps;
>  
>  extern const VhostOps user_ops;
> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
> index b1c18a3..9b76548 100644
> --- a/include/net/vhost_net.h
> +++ b/include/net/vhost_net.h
> @@ -29,4 +29,5 @@ 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, unsigned int enable);
>  #endif
> -- 
> 1.8.4.2
>