Re: [Qemu-devel] [PATCH v7 11/13] Add new vhost-user netdev backend

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

On Fri, Jan 31, 2014 at 06:34:40PM +0100, Antonios Motakis wrote:
> Add a new QEMU netdev backend that is intended to invoke vhost_net with the
> vhost-user backend.
> 
> At runtime the netdev will detect if the vhost backend is up or down. Upon
> disconnection it will set link_down accordingly and notify virtio-net. The
> virtio-net interface goes down.
> 
> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
> Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>

What happens if users try to configure e.g. e1000 with this
netdev backend?
I would expect some code in the backend checking that
frontend is virtio, but I don't see such.

> ---
>  include/net/vhost-user.h |  17 +++++++
>  net/Makefile.objs        |   2 +-
>  net/clients.h            |   3 ++
>  net/vhost-user.c         | 130 +++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 151 insertions(+), 1 deletion(-)
>  create mode 100644 include/net/vhost-user.h
>  create mode 100644 net/vhost-user.c
> 
> diff --git a/include/net/vhost-user.h b/include/net/vhost-user.h
> new file mode 100644
> index 0000000..85109f6
> --- /dev/null
> +++ b/include/net/vhost-user.h
> @@ -0,0 +1,17 @@
> +/*
> + * vhost-user.h
> + *
> + * Copyright (c) 2013 Virtual Open Systems Sarl.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef VHOST_USER_H_
> +#define VHOST_USER_H_
> +
> +struct vhost_net;
> +struct vhost_net *vhost_user_get_vhost_net(NetClientState *nc);
> +
> +#endif /* VHOST_USER_H_ */
> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index c25fe69..301f6b6 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -2,7 +2,7 @@ common-obj-y = net.o queue.o checksum.o util.o hub.o
>  common-obj-y += socket.o
>  common-obj-y += dump.o
>  common-obj-y += eth.o
> -common-obj-$(CONFIG_POSIX) += tap.o
> +common-obj-$(CONFIG_POSIX) += tap.o vhost-user.o
>  common-obj-$(CONFIG_LINUX) += tap-linux.o
>  common-obj-$(CONFIG_WIN32) += tap-win32.o
>  common-obj-$(CONFIG_BSD) += tap-bsd.o
> diff --git a/net/clients.h b/net/clients.h
> index 7322ff5..7f3d4ae 100644
> --- a/net/clients.h
> +++ b/net/clients.h
> @@ -57,4 +57,7 @@ int net_init_netmap(const NetClientOptions *opts, const char *name,
>                      NetClientState *peer);
>  #endif
>  
> +int net_init_vhost_user(const NetClientOptions *opts, const char *name,
> +                        NetClientState *peer);
> +
>  #endif /* QEMU_NET_CLIENTS_H */
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> new file mode 100644
> index 0000000..b25722c
> --- /dev/null
> +++ b/net/vhost-user.c
> @@ -0,0 +1,130 @@
> +/*
> + * vhost-user.c
> + *
> + * Copyright (c) 2013 Virtual Open Systems Sarl.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "clients.h"
> +#include "net/vhost_net.h"
> +#include "net/vhost-user.h"
> +#include "sysemu/char.h"
> +#include "qemu/error-report.h"
> +
> +typedef struct VhostUserState {
> +    NetClientState nc;
> +    CharDriverState *chr;
> +    VHostNetState *vhost_net;
> +} VhostUserState;
> +
> +VHostNetState *vhost_user_get_vhost_net(NetClientState *nc)
> +{
> +    VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
> +    return s->vhost_net;
> +}
> +
> +static int vhost_user_running(VhostUserState *s)
> +{
> +    return (s->vhost_net) ? 1 : 0;
> +}
> +
> +static int vhost_user_start(VhostUserState *s)
> +{
> +    VhostNetOptions options;
> +
> +    if (vhost_user_running(s)) {
> +        return 0;
> +    }
> +
> +    options.backend_type = VHOST_BACKEND_TYPE_USER;
> +    options.net_backend = &s->nc;
> +    options.opaque = s->chr;
> +    options.force = 1;
> +
> +    s->vhost_net = vhost_net_init(&options);
> +
> +    return vhost_user_running(s) ? 0 : -1;
> +}
> +
> +static void vhost_user_stop(VhostUserState *s)
> +{
> +    if (vhost_user_running(s)) {
> +        vhost_net_cleanup(s->vhost_net);
> +    }
> +
> +    s->vhost_net = 0;
> +}
> +
> +static void vhost_user_cleanup(NetClientState *nc)
> +{
> +    VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
> +
> +    vhost_user_stop(s);
> +    qemu_purge_queued_packets(nc);
> +}
> +
> +static NetClientInfo net_vhost_user_info = {
> +        .type = 0,
> +        .size = sizeof(VhostUserState),
> +        .cleanup = vhost_user_cleanup,
> +};
> +
> +static void net_vhost_user_event(void *opaque, int event)
> +{
> +    VhostUserState *s = opaque;
> +
> +    switch (event) {
> +    case CHR_EVENT_OPENED:
> +        vhost_user_start(s);
> +        break;
> +    case CHR_EVENT_CLOSED:
> +        s->nc.link_down = 1;
> +
> +        if (s->nc.peer) {
> +            s->nc.peer->link_down = 1;
> +        }
> +
> +        if (s->nc.info->link_status_changed) {
> +            s->nc.info->link_status_changed(&s->nc);
> +        }
> +
> +        if (s->nc.peer && s->nc.peer->info->link_status_changed) {
> +            s->nc.peer->info->link_status_changed(s->nc.peer);
> +        }
> +
> +        vhost_user_stop(s);
> +        error_report("chardev \"%s\" went down\n", s->chr->label);
> +        break;
> +    }
> +}
> +
> +static int net_vhost_user_init(NetClientState *peer, const char *device,
> +                               const char *name, CharDriverState *chr)
> +{
> +    NetClientState *nc;
> +    VhostUserState *s;
> +
> +    nc = qemu_new_net_client(&net_vhost_user_info, peer, device, name);
> +
> +    snprintf(nc->info_str, sizeof(nc->info_str), "vhost-user to %s",
> +             chr->label);
> +
> +    s = DO_UPCAST(VhostUserState, nc, nc);
> +
> +    /* We don't provide a receive callback */
> +    s->nc.receive_disabled = 1;
> +    s->chr = chr;
> +
> +    qemu_chr_add_handlers(s->chr, NULL, NULL, net_vhost_user_event, s);
> +
> +    return 0;
> +}
> +
> +int net_init_vhost_user(const NetClientOptions *opts, const char *name,
> +                   NetClientState *peer)
> +{
> +    return net_vhost_user_init(peer, "vhost_user", 0, 0);
> +}
> -- 
> 1.8.3.2
>