Re: [Qemu-devel] [RFC] net: 'Remove vhostforce option in addition to vhost param'

[Jason Wang <jasowang@redhat.com>]

On Thu, Feb 12, 2015 at 11:41 PM, Pankaj Gupta <pagupta@redhat.com> 
wrote:
>  
>>  
>>  > On Thu, Feb 12, 2015 at 11:50:05AM +0530, Pankaj Gupta wrote:
>>  > >  vhostforce was added to enable use of vhost when
>>  > >  guest don't have MSI-X support.
>>  > >  Now, we have scenarios which  dont use interrupts
>>  > >  like DPDK and still use vhost. Also, performance of
>>  > >  guests without MSI-X support is getting less popular.
>>  > > 
>>  > >  Its ok to remove this extra option and enable vhost
>>  > >  on the basis of vhost=ON/OFF.
>>  > > 
>>  > > Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>>  > 
>>  > The patch doesn't seem to do what it says.
>>  > Did you try with a non MSIX guest and vhost=on, to check that
>>  > it actually runs vhost and not userspace virtio?
>>  
>>  No, I have not. I just did basic tested a new guest without 
>> vhostforce.
>>  I will test non-MSIX guest and share the result.
> 
> I tested this with RHEL 4 guest which don't have MSI-X. Though vhost 
> gets
> created but still userspace virtio-net code executes.
> 
> So, vhostforce was added to disable vhost for non-MSI guest?

In fact to enable vhost.
> 
> I took the idea from KVM/Networking todo list.
> 
> Do we have some other dependency before we want to remove vhostforce?
>   

You may want to take a look at the vhost_dev->force and 
vhost_dev_query().
> 
>>  
>>  > 
>>  > > ---
>>  > >  net/tap.c        |  4 +---
>>  > >  net/vhost-user.c | 16 ++--------------
>>  > >  2 files changed, 3 insertions(+), 17 deletions(-)
>>  > > 
>>  > > diff --git a/net/tap.c b/net/tap.c
>>  > > index 1fe0edf..bd2efa9 100644
>>  > > --- a/net/tap.c
>>  > > +++ b/net/tap.c
>>  > > @@ -634,13 +634,11 @@ static int net_init_tap_one(const 
>> NetdevTapOptions
>>  > > *tap, NetClientState *peer,
>>  > >          }
>>  > >      }
>>  > >  
>>  > > -    if (tap->has_vhost ? tap->vhost :
>>  > > -        vhostfdname || (tap->has_vhostforce && 
>> tap->vhostforce)) {
>>  > > +    if (tap->has_vhost ? tap->vhost : vhostfdname) {
>>  > >          VhostNetOptions options;
>>  > >  
>>  > >          options.backend_type = VHOST_BACKEND_TYPE_KERNEL;
>>  > >          options.net_backend = &s->nc;
>>  > > -        options.force = tap->has_vhostforce && tap->vhostforce;
>>  > >  
>>  > >          if (tap->has_vhostfd || tap->has_vhostfds) {
>>  > >              vhostfd = monitor_handle_fd_param(cur_mon, 
>> vhostfdname);
>>  > > diff --git a/net/vhost-user.c b/net/vhost-user.c
>>  > > index 24e050c..d2d7bf2 100644
>>  > > --- a/net/vhost-user.c
>>  > > +++ b/net/vhost-user.c
>>  > > @@ -18,7 +18,6 @@
>>  > >  typedef struct VhostUserState {
>>  > >      NetClientState nc;
>>  > >      CharDriverState *chr;
>>  > > -    bool vhostforce;
>>  > >      VHostNetState *vhost_net;
>>  > >  } VhostUserState;
>>  > >  
>>  > > @@ -51,7 +50,6 @@ static int vhost_user_start(VhostUserState *s)
>>  > >      options.backend_type = VHOST_BACKEND_TYPE_USER;
>>  > >      options.net_backend = &s->nc;
>>  > >      options.opaque = s->chr;
>>  > > -    options.force = s->vhostforce;
>>  > >  
>>  > >      s->vhost_net = vhost_net_init(&options);
>>  > >  
>>  > > @@ -133,8 +131,7 @@ static void net_vhost_user_event(void 
>> *opaque, int
>>  > > event)
>>  > >  }
>>  > >  
>>  > >  static int net_vhost_user_init(NetClientState *peer, const 
>> char *device,
>>  > > -                               const char *name, 
>> CharDriverState *chr,
>>  > > -                               bool vhostforce)
>>  > > +                               const char *name, 
>> CharDriverState *chr)
>>  > >  {
>>  > >      NetClientState *nc;
>>  > >      VhostUserState *s;
>>  > > @@ -149,7 +146,6 @@ static int 
>> net_vhost_user_init(NetClientState *peer,
>>  > > const char *device,
>>  > >      /* We don't provide a receive callback */
>>  > >      s->nc.receive_disabled = 1;
>>  > >      s->chr = chr;
>>  > > -    s->vhostforce = vhostforce;
>>  > >  
>>  > >      qemu_chr_add_handlers(s->chr, NULL, NULL, 
>> net_vhost_user_event, s);
>>  > >  
>>  > > @@ -230,7 +226,6 @@ int net_init_vhost_user(const 
>> NetClientOptions *opts,
>>  > > const char *name,
>>  > >  {
>>  > >      const NetdevVhostUserOptions *vhost_user_opts;
>>  > >      CharDriverState *chr;
>>  > > -    bool vhostforce;
>>  > >  
>>  > >      assert(opts->kind == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
>>  > >      vhost_user_opts = opts->vhost_user;
>>  > > @@ -247,12 +242,5 @@ int net_init_vhost_user(const 
>> NetClientOptions
>>  > > *opts,
>>  > > const char *name,
>>  > >          return -1;
>>  > >      }
>>  > >  
>>  > > -    /* vhostforce for non-MSIX */
>>  > > -    if (vhost_user_opts->has_vhostforce) {
>>  > > -        vhostforce = vhost_user_opts->vhostforce;
>>  > > -    } else {
>>  > > -        vhostforce = false;
>>  > > -    }
>>  > > -
>>  > > -    return net_vhost_user_init(peer, "vhost_user", name, chr,
>>  > > vhostforce);
>>  > > +    return net_vhost_user_init(peer, "vhost_user", name, chr);
>>  > >  }
>>  > > --
>>  > > 1.8.3.1
>>  > 
>>  > 
>>  
>