Re: [Qemu-devel] [PATCH 5/5] Add vhost-user calls implementation

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

On Fri, Nov 29, 2013 at 08:52:26PM +0100, Antonios Motakis wrote:
> Each ioctl request of vhost-kernel has a vhost-user message equivalent,
> which is sent it over the control socket.
> 
> The general approach is to copy the data from the supplied argument
> pointer to a designated field in the message. If a file descriptor is
> to be passed it should be placed also in the fds array for inclusion in
> the sendmsd control header.

What does this code talk to? What's on the other side of the domain socket?

> VHOST_SET_MEM_TABLE ignores the supplied vhost_memory structure and scans
> the global ram_list for ram blocks wiht a valid fd field set. This would
> be set when -mem-path and -mem-prealloc command line options are used.

I don't get this.
AFAIK -mem-path is used for huge tlb fs.
So vhost-user requires huge tlb fs then?

> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>


> ---
>  hw/virtio/vhost-backend.c | 105 +++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 100 insertions(+), 5 deletions(-)
> 
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index 264a0a1..1bc2928 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -67,6 +67,38 @@ typedef struct VhostUserMsg {
>      };
>  } VhostUserMsg;
>  
> +static unsigned long int ioctl_to_vhost_user_request[VHOST_USER_MAX] = {
> +    -1, /* VHOST_USER_NONE */
> +    VHOST_GET_FEATURES, /* VHOST_USER_GET_FEATURES */
> +    VHOST_SET_FEATURES, /* VHOST_USER_SET_FEATURES */
> +    VHOST_SET_OWNER, /* VHOST_USER_SET_OWNER */
> +    VHOST_RESET_OWNER, /* VHOST_USER_RESET_OWNER */
> +    VHOST_SET_MEM_TABLE, /* VHOST_USER_SET_MEM_TABLE */
> +    VHOST_SET_LOG_BASE, /* VHOST_USER_SET_LOG_BASE */
> +    VHOST_SET_LOG_FD, /* VHOST_USER_SET_LOG_FD */
> +    VHOST_SET_VRING_NUM, /* VHOST_USER_SET_VRING_NUM */
> +    VHOST_SET_VRING_ADDR, /* VHOST_USER_SET_VRING_ADDR */
> +    VHOST_SET_VRING_BASE, /* VHOST_USER_SET_VRING_BASE */
> +    VHOST_GET_VRING_BASE, /* VHOST_USER_GET_VRING_BASE */
> +    VHOST_SET_VRING_KICK, /* VHOST_USER_SET_VRING_KICK */
> +    VHOST_SET_VRING_CALL, /* VHOST_USER_SET_VRING_CALL */
> +    VHOST_SET_VRING_ERR, /* VHOST_USER_SET_VRING_ERR */
> +    VHOST_NET_SET_BACKEND /* VHOST_USER_NET_SET_BACKEND */
> +};
> +
> +static VhostUserRequest vhost_user_request_translate(unsigned long int request)
> +{
> +    VhostUserRequest idx;
> +
> +    for (idx = 0; idx < VHOST_USER_MAX; idx++) {
> +        if (ioctl_to_vhost_user_request[idx] == request) {
> +            break;
> +        }
> +    }
> +
> +    return (idx == VHOST_USER_MAX) ? VHOST_USER_NONE : idx;
> +}
> +
>  static int vhost_user_recv(int fd, VhostUserMsg *msg)
>  {
>      ssize_t r = read(fd, msg, sizeof(VhostUserMsg));
> @@ -137,13 +169,72 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>  {
>      int fd = dev->control;
>      VhostUserMsg msg;
> -    int result = 0;
> +    RAMBlock *block = 0;
> +    int result = 0, need_reply = 0;
>      int fds[VHOST_MEMORY_MAX_NREGIONS];
>      size_t fd_num = 0;
>  
> -    memset(&msg, 0, sizeof(VhostUserMsg));
> +    msg.request = vhost_user_request_translate(request);
> +    msg.flags = 0;
>  
>      switch (request) {
> +    case VHOST_GET_FEATURES:
> +    case VHOST_GET_VRING_BASE:
> +        need_reply = 1;
> +        break;
> +
> +    case VHOST_SET_FEATURES:
> +    case VHOST_SET_LOG_BASE:
> +        msg.u64 = *((uint64_t *) arg);
> +        break;
> +
> +    case VHOST_SET_OWNER:
> +    case VHOST_RESET_OWNER:
> +        break;
> +
> +    case VHOST_SET_MEM_TABLE:
> +        QTAILQ_FOREACH(block, &ram_list.blocks, next)
> +        {
> +            if (block->fd > 0) {
> +                msg.memory.regions[fd_num].userspace_addr = (__u64) block->host;
> +                msg.memory.regions[fd_num].memory_size = block->length;
> +                msg.memory.regions[fd_num].guest_phys_addr = block->offset;
> +                fds[fd_num++] = block->fd;
> +            }
> +        }
> +
> +        msg.memory.nregions = fd_num;
> +
> +        if (!fd_num) {
> +            fprintf(stderr, "Failed initializing vhost-user memory map\n"
> +                    "consider -mem-path and -mem-prealloc options\n");
> +            return -1;
> +        }
> +        break;
> +
> +    case VHOST_SET_LOG_FD:
> +        msg.fd = *((int *) arg);
> +        break;
> +
> +    case VHOST_SET_VRING_NUM:
> +    case VHOST_SET_VRING_BASE:
> +        memcpy(&msg.state, arg, sizeof(struct vhost_vring_state));
> +        break;
> +
> +    case VHOST_SET_VRING_ADDR:
> +        memcpy(&msg.addr, arg, sizeof(struct vhost_vring_addr));
> +        break;
> +
> +    case VHOST_SET_VRING_KICK:
> +    case VHOST_SET_VRING_CALL:
> +    case VHOST_SET_VRING_ERR:
> +    case VHOST_NET_SET_BACKEND:
> +        memcpy(&msg.file, arg, sizeof(struct vhost_vring_file));
> +        if (msg.file.fd > 0) {
> +            fds[0] = msg.file.fd;
> +            fd_num = 1;
> +        }
> +        break;
>      default:
>          fprintf(stderr, "vhost-user trying to send unhandled ioctl\n");
>          return -1;
> @@ -152,12 +243,16 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
>  
>      result = vhost_user_send_fds(fd, &msg, fds, fd_num);
>  
> -    if (!result) {
> +    if (!result && need_reply) {
>          result = vhost_user_recv(fd, &msg);
>          if (!result) {
>              switch (request) {
> -            default:
> -                fprintf(stderr, "vhost-user received unhandled message\n");
> +            case VHOST_GET_FEATURES:
> +                *((uint64_t *) arg) = msg.u64;
> +                break;
> +            case VHOST_GET_VRING_BASE:
> +                memcpy(arg, &msg.state, sizeof(struct vhost_vring_state));
> +                break;
>              }
>          }
>      }
> -- 
> 1.8.3.2
>