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


From: Jason Wang
Subject: Re: [Qemu-devel] [RFC] net: 'Remove vhostforce option in addition to vhost param'
Date: Sun, 15 Feb 2015 02:49:29 +0008



On Thu, Feb 12, 2015 at 11:41 PM, Pankaj Gupta <address@hidden> 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 <address@hidden> > > 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
> >





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