[Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options

[Anthony Liguori]

On 02/25/2010 12:28 PM, Michael S. Tsirkin wrote:
> This adds vhost binary option to tap, to enable vhost net accelerator.
> Default is off for now, we'll be able to make default on long term
> when we know it's stable.
>
> vhostfd option can be used by management, to pass in the fd. Assigning
> vhostfd implies vhost=on.
>
> Signed-off-by: Michael S. Tsirkin<address@hidden>
>    

Since the thinking these days is that macvtap and tap is pretty much all 
we'll ever need for vhost-net, perhaps we should revisit -net vhost vs. 
-net tap,vhost=X?

I think -net vhost,fd=X makes a lot more sense than -net 
tap,vhost=on,vhostfd=X.

Regards,

Anthony Liguori

> ---
>   net.c           |    8 ++++++++
>   net/tap.c       |   33 +++++++++++++++++++++++++++++++++
>   qemu-options.hx |    4 +++-
>   3 files changed, 44 insertions(+), 1 deletions(-)
>
> diff --git a/net.c b/net.c
> index a1bf49f..d1e23f1 100644
> --- a/net.c
> +++ b/net.c
> @@ -973,6 +973,14 @@ static const struct {
>                   .name = "vnet_hdr",
>                   .type = QEMU_OPT_BOOL,
>                   .help = "enable the IFF_VNET_HDR flag on the tap interface"
> +            }, {
> +                .name = "vhost",
> +                .type = QEMU_OPT_BOOL,
> +                .help = "enable vhost-net network accelerator",
> +            }, {
> +                .name = "vhostfd",
> +                .type = QEMU_OPT_STRING,
> +                .help = "file descriptor of an already opened vhost net 
> device",
>               },
>   #endif /* _WIN32 */
>               { /* end of list */ }
> diff --git a/net/tap.c b/net/tap.c
> index fc59fd4..65797ef 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -41,6 +41,8 @@
>
>   #include "net/tap-linux.h"
>
> +#include "hw/vhost_net.h"
> +
>   /* Maximum GSO packet size (64k) plus plenty of room for
>    * the ethernet and virtio_net headers
>    */
> @@ -57,6 +59,7 @@ typedef struct TAPState {
>       unsigned int has_vnet_hdr : 1;
>       unsigned int using_vnet_hdr : 1;
>       unsigned int has_ufo: 1;
> +    struct vhost_net *vhost_net;
>   } TAPState;
>
>   static int launch_script(const char *setup_script, const char *ifname, int 
> fd);
> @@ -252,6 +255,10 @@ static void tap_cleanup(VLANClientState *nc)
>   {
>       TAPState *s = DO_UPCAST(TAPState, nc, nc);
>
> +    if (s->vhost_net) {
> +        vhost_net_cleanup(s->vhost_net);
> +    }
> +
>       qemu_purge_queued_packets(nc);
>
>       if (s->down_script[0])
> @@ -307,6 +314,7 @@ static TAPState *net_tap_fd_init(VLANState *vlan,
>       s->has_ufo = tap_probe_has_ufo(s->fd);
>       tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
>       tap_read_poll(s, 1);
> +    s->vhost_net = NULL;
>       return s;
>   }
>
> @@ -456,5 +464,30 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char 
> *name, VLANState *vlan
>           }
>       }
>
> +    if (qemu_opt_get_bool(opts, "vhost", !!qemu_opt_get(opts, "vhostfd"))) {
> +        int vhostfd, r;
> +        if (qemu_opt_get(opts, "vhostfd")) {
> +            r = net_handle_fd_param(mon, qemu_opt_get(opts, "vhostfd"));
> +            if (r == -1) {
> +                return -1;
> +            }
> +            vhostfd = r;
> +        } else {
> +            vhostfd = -1;
> +        }
> +        s->vhost_net = vhost_net_init(&s->nc, vhostfd);
> +        if (!s->vhost_net) {
> +            qemu_error("vhost-net requested but could not be initialized\n");
> +            return -1;
> +        }
> +    } else if (qemu_opt_get(opts, "vhostfd")) {
> +        qemu_error("vhostfd= is not valid without vhost\n");
> +        return -1;
> +    }
> +
> +    if (vlan) {
> +        vlan->nb_host_devs++;
> +    }
> +
>       return 0;
>   }
> diff --git a/qemu-options.hx b/qemu-options.hx
> index f53922f..1850906 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -879,7 +879,7 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
>       "-net tap[,vlan=n][,name=str],ifname=name\n"
>       "                connect the host TAP network interface to VLAN 'n'\n"
>   #else
> -    "-net 
> tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,sndbuf=nbytes][,vnet_hdr=on|off]\n"
> +    "-net 
> tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h]\n"
>       "                connect the host TAP network interface to VLAN 'n' and use 
> the\n"
>       "                network scripts 'file' (default=" DEFAULT_NETWORK_SCRIPT 
> ")\n"
>       "                and 'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
> @@ -889,6 +889,8 @@ DEF("net", HAS_ARG, QEMU_OPTION_net,
>       "                default of 'sndbuf=1048576' can be disabled using 
> 'sndbuf=0')\n"
>       "                use vnet_hdr=off to avoid enabling the IFF_VNET_HDR tap 
> flag\n"
>       "                use vnet_hdr=on to make the lack of IFF_VNET_HDR support an 
> error condition\n"
> +    "                use vhost=on to enable experimental in kernel 
> accelerator\n"
> +    "                use 'vhostfd=h' to connect to an already opened vhost net 
> device\n"
>   #endif
>       "-net 
> socket[,vlan=n][,name=str][,fd=h][,listen=[host]:port][,connect=host:port]\n"
>       "                connect the vlan 'n' to another VLAN using a socket 
> connection\n"
>