[Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Feb 25, 2010 at 08:04:21PM +0100, Juan Quintela wrote:
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > This adds vhost net device support in qemu. Will be tied to tap device
> > and virtio by following patches.  Raw backend is currently missing,
> > will be worked on/submitted separately.
> >
> 
> +obj-y += vhost_net.o
> +obj-$(CONFIG_VHOST_NET) += vhost.o
> 
> hy is vhost_net.o configured unconditionally?


It includes stubs that return error. This way callers do not
need to include any ifdefs.

> > --- a/configure
> > +++ b/configure
> > @@ -1498,6 +1498,23 @@ EOF
> >  fi
> >
> This misses vhost_net var definition at the start of the file

Seems to work without. Why is it needed?

> and
> --enable-vhost/--disable-vhost options.
> 

I don't really see why we need --enable-vhost/--disable-vhost.
Runtime flag is enough.

> >  ##########################################
> > +# test for vhost net
> > +
> > +if test "$kvm" != "no"; then
> > +	cat > $TMPC <<EOF
> > +#include <linux/vhost.h>
> > +int main(void) { return 0; }
> > +EOF
> > +	if compile_prog "$kvm_cflags" "" ; then
> > +	vhost_net=yes
> > +	else
> > +	vhost_net=no
> > +	fi
> 
> Indent please.
> 
> > +else
> > +	vhost_net=no
> > +fi
> > +
> > +##########################################
> >  # pthread probe
> >  PTHREADLIBS_LIST="-lpthread -lpthreadGC2"
> >  
> > @@ -1968,6 +1985,7 @@ echo "fdt support       $fdt"
> >  echo "preadv support    $preadv"
> >  echo "fdatasync         $fdatasync"
> >  echo "uuid support      $uuid"
> > +echo "vhost-net support $vhost_net"
> 
> Otherwise this couldo not be there.


What do you mean? vhost_net always gets a value, so it is safe to use
here.

> >  if test $sdl_too_old = "yes"; then
> >  echo "-> Your SDL version is too old - please upgrade to have SDL support"
> > @@ -2492,6 +2510,9 @@ case "$target_arch2" in
> >        if test "$kvm_para" = "yes"; then
> >          echo "CONFIG_KVM_PARA=y" >> $config_target_mak
> >        fi
> > +      if test $vhost_net = "yes" ; then
> > +        echo "CONFIG_VHOST_NET=y" >> $config_target_mak
> > +      fi
> >      fi
> >  esac
> >  echo "TARGET_PHYS_ADDR_BITS=$target_phys_bits" >> $config_target_mak
> 
> > +    for (;from < to; ++from) {
> > +        vhost_log_chunk_t log;
> 
> .....
> 
> > +                ffsll(log) : ffs(log))) {
> 
>   if you defines vhost_log_chuck_t, you also define vhost_log_ffs() and
>   you are done without this if.
> 
> Later, Juan.