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

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

On Thu, Feb 25, 2010 at 01:47:27PM -0600, Anthony Liguori wrote:
> 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<mst@redhat.com>
>>    
>
> 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

We'll have to duplicate all tap options.
I think long term we will just make vhost=on the default.
Users do not really care about vhost, it just makes tap
go fater. So promoting it to 1st class options is wrong IMO.

>> ---
>>   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"
>>