On Mon, 31 Aug 2020 at 16:30, Jason Wang <jasow...@redhat.com> wrote:
>
> This patch allows to initialize vhost-vdpa network backend with pre
> opened vhost-vdpa file descriptor. This is useful for running
> unprivileged qemu through libvirt.
>
> Cc: Eric Blake <ebl...@redhat.com>
> Cc: Markus Armbruster <arm...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> net/vhost-vdpa.c | 24 +++++++++++++++++++-----
> qapi/net.json | 5 ++++-
> 2 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 9a6f0b63d3..f6385cd264 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -206,20 +206,34 @@ int net_init_vhost_vdpa(const Netdev *netdev, const
> char *name,
> (char *)name, errp)) {
> return -1;
> }
> - if (!opts->has_vhostdev) {
> - error_setg(errp, "vhost-vdpa requires vhostdev to be set");
> + if (!(opts->has_vhostdev ^ opts->has_fd)) {
> + error_setg(errp, "Vhost-vdpa requires either vhostdev or fd to be
> set");
> return -1;
> }
>
> assert(name);
>
> nc = qemu_new_net_client(&net_vhost_vdpa_info, peer, TYPE_VHOST_VDPA,
> name);
> - snprintf(nc->info_str, sizeof(nc->info_str), "vhostdev=%s",
> opts->vhostdev);
> + if (opts->has_vhostdev) {
> + snprintf(nc->info_str, sizeof(nc->info_str),
> + "vhostdev=%s", opts->vhostdev);
> + vdpa_device_fd = qemu_open(opts->vhostdev, O_RDWR);
> + if (vdpa_device_fd == -1) {
> + error_setg(errp, "Fail to open vhost-vdpa device %s",
> + opts->vhostdev);
> + return -errno;
> + }
> + } else {
> + snprintf(nc->info_str, sizeof(nc->info_str), "fd=%s", opts->fd);
> + vdpa_device_fd = monitor_fd_param(cur_mon, opts->fd, errp);
> + if (vdpa_device_fd == -1) {
> + return -1;
> + }
> + }
>
> s = DO_UPCAST(VhostVDPAState, nc, nc);
> - vdpa_device_fd = qemu_open(opts->vhostdev, O_RDWR);
> if (vdpa_device_fd == -1) {
> - error_setg(errp, "Fail to open vhost-vdpa device %s",
> opts->vhostdev);
> +
> return -errno;
> }
> s->vhost_vdpa.device_fd = vdpa_device_fd;
> diff --git a/qapi/net.json b/qapi/net.json
> index a2a94fad3e..5ad60c3045 100644
> --- a/qapi/net.json
> +++ b/qapi/net.json
> @@ -442,12 +442,15 @@
> # @queues: number of queues to be created for multiqueue vhost-vdpa
> # (default: 1)
> #
> +# @fd: file descriptor of an already opened vhost-vdpa (since 5.2)
> +#
> # Since: 5.1
> ##
> { 'struct': 'NetdevVhostVDPAOptions',
> 'data': {
> '*vhostdev': 'str',
> - '*queues': 'int' } }
> + '*queues': 'int',
> + '*fd': 'str' } }
>
> ##
> # @NetClientDriver:
> --
> 2.20.1
>
I think the latest code supported this part.
you can pass a pre open file descriptor to it via the add-fd QMP
command to /dev/fdset/NNN, and then pass the string
"/dev/fdset/NNN" as vhostdev. so we don't need a special fd parameter here.
Thanks
Cindy
