Re: [Qemu-devel] [PATCH 02/71] vhost-net-user: add stubs for when no virtio-net device is present

[Thomas Huth]

On 2018-12-03 16:32, Paolo Bonzini wrote:
> hw/net/vhost_net.c needs functions that are declared in net/vhost-user.c: the
> vhost-user code is always compiled into QEMU, only the constructor
> net_init_vhost_user is unreachable.  Also, net/vhost-user.c needs functions
> declared in hw/virtio/vhost-stub.c even if no virtio device exists.
> 
> Break this dependency.  First, add a minimal version of net/vhost-user.c,
> with no functionality and no dependency on vhost code.  Second, #ifdef out
> the calls back to net/vhost-user.c from hw/net/vhost_net.c.
> 
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  configure             |  2 +-
>  hw/net/vhost_net.c    |  4 ++++
>  net/Makefile.objs     |  4 +++-
>  net/net.c             |  2 +-
>  net/vhost-user-stub.c | 23 +++++++++++++++++++++++
>  5 files changed, 32 insertions(+), 3 deletions(-)
>  create mode 100644 net/vhost-user-stub.c
> 
> diff --git a/configure b/configure
> index 0a3c6a7..cda17ef 100755
> --- a/configure
> +++ b/configure
> @@ -6513,7 +6513,7 @@ if test "$vhost_scsi" = "yes" ; then
>    echo "CONFIG_VHOST_SCSI=y" >> $config_host_mak
>  fi
>  if test "$vhost_net" = "yes" -a "$vhost_user" = "yes"; then
> -  echo "CONFIG_VHOST_NET_USED=y" >> $config_host_mak
> +  echo "CONFIG_VHOST_NET_USER=y" >> $config_host_mak

Maybe mention this in the patch description, too?

>  fi
>  if test "$vhost_crypto" = "yes" ; then
>    echo "CONFIG_VHOST_CRYPTO=y" >> $config_host_mak
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index b901306..fe6202a 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -193,6 +193,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
>      }
>  
>      /* Set sane init value. Override when guest acks. */
> +#ifdef CONFIG_VHOST_USER
>      if (net->nc->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
>          features = vhost_user_get_acked_features(net->nc);
>          if (~net->dev.features & features) {
> @@ -202,6 +203,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
>              goto fail;
>          }
>      }
> +#endif
>  
>      vhost_net_ack_features(net, features);
>  
> @@ -413,10 +415,12 @@ VHostNetState *get_vhost_net(NetClientState *nc)
>      case NET_CLIENT_DRIVER_TAP:
>          vhost_net = tap_get_vhost_net(nc);
>          break;
> +#ifdef CONFIG_VHOST_NET_USER
>      case NET_CLIENT_DRIVER_VHOST_USER:
>          vhost_net = vhost_user_get_vhost_net(nc);
>          assert(vhost_net);
>          break;
> +#endif
>      default:
>          break;
>      }
> diff --git a/net/Makefile.objs b/net/Makefile.objs
> index b2bf88a..df2b409 100644
> --- a/net/Makefile.objs
> +++ b/net/Makefile.objs
> @@ -3,7 +3,9 @@ common-obj-y += socket.o
>  common-obj-y += dump.o
>  common-obj-y += eth.o
>  common-obj-$(CONFIG_L2TPV3) += l2tpv3.o
> -common-obj-$(CONFIG_POSIX) += vhost-user.o
> +common-obj-$(call land,$(CONFIG_VIRTIO_NET),$(CONFIG_VHOST_NET_USER)) += 
> vhost-user.o
> +common-obj-$(call land,$(call 
> lnot,$(CONFIG_VIRTIO_NET)),$(CONFIG_VHOST_NET_USER)) += vhost-user-stub.o
> +common-obj-$(CONFIG_ALL) += vhost-user-stub.o
>  common-obj-$(CONFIG_SLIRP) += slirp.o
>  common-obj-$(CONFIG_VDE) += vde.o
>  common-obj-$(CONFIG_NETMAP) += netmap.o
> diff --git a/net/net.c b/net/net.c
> index 07c194a..95a74ad 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -955,7 +955,7 @@ static int (* const 
> net_client_init_fun[NET_CLIENT_DRIVER__MAX])(
>          [NET_CLIENT_DRIVER_BRIDGE]    = net_init_bridge,
>  #endif
>          [NET_CLIENT_DRIVER_HUBPORT]   = net_init_hubport,
> -#ifdef CONFIG_VHOST_NET_USED
> +#ifdef CONFIG_VHOST_NET_USER
>          [NET_CLIENT_DRIVER_VHOST_USER] = net_init_vhost_user,
>  #endif
>  #ifdef CONFIG_L2TPV3
> diff --git a/net/vhost-user-stub.c b/net/vhost-user-stub.c
> new file mode 100644
> index 0000000..52ab4e1
> --- /dev/null
> +++ b/net/vhost-user-stub.c
> @@ -0,0 +1,23 @@
> +/*
> + * vhost-user-stub.c
> + *
> + * Copyright (c) 2018 Red Hat, Inc.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +#include "clients.h"
> +#include "net/vhost_net.h"
> +#include "net/vhost-user.h"
> +#include "qemu/error-report.h"
> +#include "qapi/error.h"
> +
> +int net_init_vhost_user(const Netdev *netdev, const char *name,
> +                        NetClientState *peer, Error **errp)
> +{
> +    error_setg(errp, "vhost-user requires frontend driver virtio-net-*");
> +    return -1;
> +}
> 

It's a little bit sad that we need the stub in this case, but since
CONFIG_VIRTIO_NET is not available as a CPP macro, I also don't have any
better ideas.

Reviewed-by: Thomas Huth <address@hidden>