Re: [Qemu-devel] [PATCH 2/6] Revert "vhost-net: tell tap backend about the vnet endianness"

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Thu, 7 Jan 2016 20:52:04 +0100
Laurent Vivier <lvivier@redhat.com> wrote:

> 
> 
> On 07/01/2016 12:32, Greg Kurz wrote:
> > This reverts commit 5be7d9f1b1452613b95c6ba70b8d7ad3d0797991.
> > 
> > Cross-endian is now configured by the core virtio-net code. We simply
> > fall back on full emulation if the net backend cannot support the
> > requested endianness for vnet headers.
> > 
> > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > ---
> >  hw/net/vhost_net.c  |   33 +--------------------------------
> >  hw/net/virtio-net.c |    7 +++++++
> >  2 files changed, 8 insertions(+), 32 deletions(-)
> > 
> > diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> > index 318c3e6ad213..0c7362b7a772 100644
> > --- a/hw/net/vhost_net.c
> > +++ b/hw/net/vhost_net.c
> > @@ -38,7 +38,6 @@
> >  #include "standard-headers/linux/virtio_ring.h"
> >  #include "hw/virtio/vhost.h"
> >  #include "hw/virtio/virtio-bus.h"
> > -#include "hw/virtio/virtio-access.h"
> >  
> >  struct vhost_net {
> >      struct vhost_dev dev;
> > @@ -199,27 +198,6 @@ static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index)
> >      net->dev.vq_index = vq_index;
> >  }
> >  
> > -static int vhost_net_set_vnet_endian(VirtIODevice *dev, NetClientState *peer,
> > -                                     bool set)
> > -{
> > -    int r = 0;
> > -
> > -    if (virtio_vdev_has_feature(dev, VIRTIO_F_VERSION_1) ||
> > -        (virtio_legacy_is_cross_endian(dev) && !virtio_is_big_endian(dev))) {
> > -        r = qemu_set_vnet_le(peer, set);
> > -        if (r) {
> > -            error_report("backend does not support LE vnet headers");
> > -        }
> > -    } else if (virtio_legacy_is_cross_endian(dev)) {
> > -        r = qemu_set_vnet_be(peer, set);
> > -        if (r) {
> > -            error_report("backend does not support BE vnet headers");
> > -        }
> > -    }
> > -
> > -    return r;
> > -}
> > -
> >  static int vhost_net_start_one(struct vhost_net *net,
> >                                 VirtIODevice *dev)
> >  {
> > @@ -308,11 +286,6 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
> >          goto err;
> >      }
> >  
> > -    r = vhost_net_set_vnet_endian(dev, ncs[0].peer, true);
> > -    if (r < 0) {
> > -        goto err;
> > -    }
> > -
> >      for (i = 0; i < total_queues; i++) {
> >          vhost_net_set_vq_index(get_vhost_net(ncs[i].peer), i * 2);
> >      }
> > @@ -320,7 +293,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
> >      r = k->set_guest_notifiers(qbus->parent, total_queues * 2, true);
> >      if (r < 0) {
> >          error_report("Error binding guest notifier: %d", -r);
> > -        goto err_endian;
> > +        goto err;
> >      }
> >  
> >      for (i = 0; i < total_queues; i++) {
> > @@ -342,8 +315,6 @@ err_start:
> >          fprintf(stderr, "vhost guest notifier cleanup failed: %d\n", e);
> >          fflush(stderr);
> >      }
> > -err_endian:
> > -    vhost_net_set_vnet_endian(dev, ncs[0].peer, false);
> >  err:
> >      return r;
> >  }
> > @@ -366,8 +337,6 @@ void vhost_net_stop(VirtIODevice *dev, NetClientState *ncs,
> >          fflush(stderr);
> >      }
> >      assert(r >= 0);
> > -
> > -    assert(vhost_net_set_vnet_endian(dev, ncs[0].peer, false) >= 0);
> >  }
> >  
> >  void vhost_net_cleanup(struct vhost_net *net)
> > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > index d4cc94ea5e55..5a0ab6ad5bb5 100644
> > --- a/hw/net/virtio-net.c
> > +++ b/hw/net/virtio-net.c
> > @@ -128,6 +128,13 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
> >      if (!n->vhost_started) {
> >          int r, i;
> >  
> > +        if (n->needs_vnet_hdr_swap) {
> > +            error_report("backend does not support %s vnet headers."
> > +                         "falling back on userspace virtio",
> > +                         virtio_is_big_endian(vdev) ? "BE" : "LE");
> > +            return;
> > +        }
> > +
> 
> This is not part of the revert, perhaps this can go in PATCH 1/6 ?
> In virtio_net_vnet_status() ?
> 

Makes sense. I'll fix that.

> >          /* Any packets outstanding? Purge them to avoid touching rings
> >           * when vhost is running.
> >           */
> > 
> > 
>