Re: [Qemu-devel] [RFC] libvhost-user: implement VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS

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

On Fri, Sep 06, 2019 at 03:13:50PM +0300, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
> 
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>

a bit more content here about the motivation for this?

> ---
>  contrib/libvhost-user/libvhost-user.c | 61 +++++++++++++++++++++++----
>  contrib/libvhost-user/libvhost-user.h |  3 ++
>  2 files changed, 56 insertions(+), 8 deletions(-)
> 
> diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
> index fba291c13db4..550f6416a211 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -136,6 +136,7 @@ vu_request_to_string(unsigned int req)
>          REQ(VHOST_USER_GET_INFLIGHT_FD),
>          REQ(VHOST_USER_SET_INFLIGHT_FD),
>          REQ(VHOST_USER_GPU_SET_SOCKET),
> +        REQ(VHOST_USER_VRING_KICK),
>          REQ(VHOST_USER_MAX),
>      };
>  #undef REQ
> @@ -920,6 +921,7 @@ static bool
>  vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
>  {
>      int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> +    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
>  
>      if (index >= dev->max_queues) {
>          vmsg_close_fds(vmsg);
> @@ -927,8 +929,12 @@ vu_check_queue_msg_file(VuDev *dev, VhostUserMsg *vmsg)
>          return false;
>      }
>  
> -    if (vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK ||
> -        vmsg->fd_num != 1) {
> +    if (nofd) {
> +        vmsg_close_fds(vmsg);
> +        return true;
> +    }
> +
> +    if (vmsg->fd_num != 1) {
>          vmsg_close_fds(vmsg);
>          vu_panic(dev, "Invalid fds in request: %d", vmsg->request);
>          return false;
> @@ -1025,6 +1031,7 @@ static bool
>  vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
>  {
>      int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> +    bool nofd = vmsg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
>  
>      DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
>  
> @@ -1038,8 +1045,8 @@ vu_set_vring_kick_exec(VuDev *dev, VhostUserMsg *vmsg)
>          dev->vq[index].kick_fd = -1;
>      }
>  
> -    dev->vq[index].kick_fd = vmsg->fds[0];
> -    DPRINT("Got kick_fd: %d for vq: %d\n", vmsg->fds[0], index);
> +    dev->vq[index].kick_fd = nofd ? -1 : vmsg->fds[0];
> +    DPRINT("Got kick_fd: %d for vq: %d\n", dev->vq[index].kick_fd, index);
>  
>      dev->vq[index].started = true;
>      if (dev->iface->queue_set_started) {
> @@ -1116,6 +1123,7 @@ static bool
>  vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
>  {
>      int index = vmsg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
> +    bool nofd = VHOST_USER_VRING_NOFD_MASK;
>  
>      DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
>  
> @@ -1128,14 +1136,14 @@ vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg)
>          dev->vq[index].call_fd = -1;
>      }
>  
> -    dev->vq[index].call_fd = vmsg->fds[0];
> +    dev->vq[index].call_fd = nofd ? -1 : vmsg->fds[0];
>  
>      /* in case of I/O hang after reconnecting */
> -    if (eventfd_write(vmsg->fds[0], 1)) {
> +    if (dev->vq[index].call_fd != -1 && eventfd_write(vmsg->fds[0], 1)) {
>          return -1;
>      }
>  
> -    DPRINT("Got call_fd: %d for vq: %d\n", vmsg->fds[0], index);
> +    DPRINT("Got call_fd: %d for vq: %d\n", dev->vq[index].call_fd, index);
>  
>      return false;
>  }
> @@ -1169,7 +1177,8 @@ vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
>                          1ULL << VHOST_USER_PROTOCOL_F_SLAVE_REQ |
>                          1ULL << VHOST_USER_PROTOCOL_F_HOST_NOTIFIER |
>                          1ULL << VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD |
> -                        1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK;
> +                        1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK |
> +                        1ULL << VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS;
>  
>      if (have_userfault()) {
>          features |= 1ULL << VHOST_USER_PROTOCOL_F_PAGEFAULT;
> @@ -1456,6 +1465,25 @@ vu_set_inflight_fd(VuDev *dev, VhostUserMsg *vmsg)
>      return false;
>  }
>  
> +static bool
> +vu_handle_vring_kick(VuDev *dev, VhostUserMsg *vmsg)
> +{
> +    unsigned int index = vmsg->payload.state.index;
> +
> +    if (index >= dev->max_queues) {
> +        vu_panic(dev, "Invalid queue index: %u", index);
> +        return false;
> +    }
> +
> +    DPRINT("Got kick message: handler:%p idx:%d\n",
> +	   dev->vq[index].handler, index);
> +    if (dev->vq[index].handler) {
> +        dev->vq[index].handler(dev, index);
> +    }
> +
> +    return false;
> +}
> +
>  static bool
>  vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
>  {
> @@ -1538,6 +1566,8 @@ vu_process_message(VuDev *dev, VhostUserMsg *vmsg)
>          return vu_get_inflight_fd(dev, vmsg);
>      case VHOST_USER_SET_INFLIGHT_FD:
>          return vu_set_inflight_fd(dev, vmsg);
> +    case VHOST_USER_VRING_KICK:
> +        return vu_handle_vring_kick(dev, vmsg);
>      default:
>          vmsg_close_fds(vmsg);
>          vu_panic(dev, "Unhandled request: %d", vmsg->request);
> @@ -2010,6 +2040,21 @@ vu_queue_notify(VuDev *dev, VuVirtq *vq)
>          return;
>      }
>  
> +    if (vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS) &&
> +        vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SLAVE_REQ)) {
> +        VhostUserMsg vmsg = {
> +            .request = VHOST_USER_SLAVE_VRING_CALL,
> +            .flags = VHOST_USER_VERSION,
> +            .size = sizeof(vmsg.payload.state),
> +            .payload.state = {
> +                .index = dev->vq - vq,
> +            },
> +        };
> +
> +        vu_message_write(dev, dev->slave_fd, &vmsg);
> +        return;
> +    }
> +
>      if (eventfd_write(vq->call_fd, 1) < 0) {
>          vu_panic(dev, "Error writing eventfd: %s", strerror(errno));
>      }
> diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
> index 46b600799b2e..392dea306bb9 100644
> --- a/contrib/libvhost-user/libvhost-user.h
> +++ b/contrib/libvhost-user/libvhost-user.h
> @@ -53,6 +53,7 @@ enum VhostUserProtocolFeature {
>      VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
>      VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
>      VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
> +    VHOST_USER_PROTOCOL_F_KICK_CALL_MSGS = 13,
>  
>      VHOST_USER_PROTOCOL_F_MAX
>  };
> @@ -94,6 +95,7 @@ typedef enum VhostUserRequest {
>      VHOST_USER_GET_INFLIGHT_FD = 31,
>      VHOST_USER_SET_INFLIGHT_FD = 32,
>      VHOST_USER_GPU_SET_SOCKET = 33,
> +    VHOST_USER_VRING_KICK = 34,
>      VHOST_USER_MAX
>  } VhostUserRequest;
>  
> @@ -102,6 +104,7 @@ typedef enum VhostUserSlaveRequest {
>      VHOST_USER_SLAVE_IOTLB_MSG = 1,
>      VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
>      VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
> +    VHOST_USER_SLAVE_VRING_CALL = 4,
>      VHOST_USER_SLAVE_MAX
>  }  VhostUserSlaveRequest;
>  
> -- 
> 2.23.0
>