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

[Pankaj Gupta <pagupta@redhat.com>]

 
> 
> > 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?
I took the idea from KVM/Networking todo list.

Do we have some other dependency before we want to remove vhostforce?
  
> 
> > 
> > > ---
> > >  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
> > 
> > 
>