Re: [Qemu-devel] [PATCH v4] tap: setting error appropriately when calling net_init_tap_one()

[Zhoujian (jay)]

> -----Original Message-----
> From: Jason Wang [mailto:address@hidden
> Sent: Friday, March 02, 2018 2:30 PM
> To: Zhoujian (jay) <address@hidden>; address@hidden
> Cc: Huangweidong (C) <address@hidden>; address@hidden; Gonglei
> (Arei) <address@hidden>; address@hidden; wangxin (U)
> <address@hidden>
> Subject: Re: [Qemu-devel] [PATCH v4] tap: setting error appropriately when
> calling net_init_tap_one()
> 
> 
> 
> On 2018年02月06日 20:53, Jay Zhou wrote:
> > If netdev_add tap,id=net0,...,vhost=on failed in net_init_tap_one(),
> > the followed up device_add virtio-net-pci,netdev=net0 will fail too,
> > prints:
> >
> >     TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD
> >     ioctl() failed: Bad file descriptor
> >
> > The reason is that the fd of tap is closed when error occured after
> > calling net_init_tap_one().
> >
> > The fd should be closed when calling net_init_tap_one failed:
> >     - if tap_set_sndbuf() failed
> >     - if tap_set_sndbuf() succeeded but vhost failed to open or
> >       initialize with vhostforce flag on The fd should not be closed
> > just because vhost failed to open or initialize but without vhostforce
> > flag. So the followed up device_add can fall back to userspace virtio
> > successfully.
> >
> > Suggested-by: Michael S. Tsirkin <address@hidden>
> > Suggested-by: Igor Mammedov <address@hidden>
> > Suggested-by: Jason Wang <address@hidden>
> > Signed-off-by: Jay Zhou <address@hidden>
> > ---
> > v4: - reduce duplication
> >      - close the fd by caller
> >      - tweak the title
> >
> > v3: - set errp appropriately
> > ---
> >   include/net/vhost_net.h |  3 +++
> >   net/tap.c               | 24 ++++++++++++++++++------
> >   2 files changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h index
> > afc1499..77e4739 100644
> > --- a/include/net/vhost_net.h
> > +++ b/include/net/vhost_net.h
> > @@ -4,6 +4,9 @@
> >   #include "net/net.h"
> >   #include "hw/virtio/vhost-backend.h"
> >
> > +#define VHOST_NET_INIT_FAILED \
> > +    "vhost-net requested but could not be initialized"
> > +
> >   struct vhost_net;
> >   typedef struct vhost_net VHostNetState;
> >
> > diff --git a/net/tap.c b/net/tap.c
> > index 979e622..14d230f 100644
> > --- a/net/tap.c
> > +++ b/net/tap.c
> > @@ -686,14 +686,23 @@ static void net_init_tap_one(const NetdevTapOptions
> *tap, NetClientState *peer,
> >           if (vhostfdname) {
> >               vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);
> >               if (vhostfd == -1) {
> > -                error_propagate(errp, err);
> > +                if (tap->has_vhostforce && tap->vhostforce) {
> > +                    error_propagate(errp, err);
> > +                } else {
> > +                    warn_report_err(err);
> > +                }
> >                   return;
> >               }
> >           } else {
> >               vhostfd = open("/dev/vhost-net", O_RDWR);
> >               if (vhostfd < 0) {
> > -                error_setg_errno(errp, errno,
> > -                                 "tap: open vhost char device failed");
> > +                if (tap->has_vhostforce && tap->vhostforce) {
> > +                    error_setg_errno(errp, errno,
> > +                                     "tap: open vhost char device failed");
> > +                } else {
> > +                    warn_report("tap: open vhost char device failed: %s",
> > +                                strerror(errno));
> > +                }
> >                   return;
> >               }
> >               fcntl(vhostfd, F_SETFL, O_NONBLOCK); @@ -702,12 +711,15
> > @@ static void net_init_tap_one(const NetdevTapOptions *tap,
> > NetClientState *peer,
> >
> >           s->vhost_net = vhost_net_init(&options);
> >           if (!s->vhost_net) {
> > -            error_setg(errp,
> > -                       "vhost-net requested but could not be initialized");
> > +            if (tap->has_vhostforce && tap->vhostforce) {
> > +                error_setg(errp, VHOST_NET_INIT_FAILED);
> > +            } else {
> > +                warn_report(VHOST_NET_INIT_FAILED);
> > +            }
> >               return;
> >           }
> >       } else if (vhostfdname) {
> > -        error_setg(errp, "vhostfd(s)= is not valid without vhost");
> > +        warn_report("vhostfd(s)= is not valid without vhost");
> 
> Do we need to keep the error here consider it was a wrong command line
> parameter?

Fair enough, thanks!

Regards,
Jay

> 
> Thanks
> 
> >       }
> >   }
> >