SR-IOV and Intel X520 82599ES

Does anyone have prior experience configuring SR-IOV with Intel ix(4)
driver? I followed the instructions:

Setup config files:

# cat /etc/sr-iov/ix0.conf
PF
{
  device : ix0;
  num_vfs: 4;
}
DEFAULT
{
  allow-set-mac: true;
  allow-promisc: true;
}

# cat /etc/sr-iov/ix1.conf
PF
{
  device : ix1;
  num_vfs: 4;
}
DEFAULT                                                                                             
{
  allow-set-mac: true;
  allow-promisc: true;
}

Execute iovctl:

# iovctl -C -f /etc/sr-iov/ix0.conf
# iovctl -C -f /etc/sr-iov/ix1.conf

I can see various ixv* interfaces allocated:

ixv0: <Intel(R) X520 82599 Virtual Function> at device 0.128 on pci3
ixv0: Using 2048 TX descriptors and 2048 RX descriptors
ixv0: Using 1 RX queues 1 TX queues
ixv0: Using MSI-X interrupts with 2 vectors
ixv0: allocated for 1 queues
ixv0: allocated for 1 rx queues
ixv0: Ethernet address: 58:9c:fc:00:26:26
ixv0: link state changed to UP
ixv0: netmap queues/slots: TX 1/2048, RX 1/2048

root@jail1:~ # ifconfig ixv0
ixv0: flags=1008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LOWER_UP> metric 0 mtu 9000
        options=4e507bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6,HWSTATS,MEXTPG>
        ether 58:9c:fc:00:26:26
        inet 192.168.10.50 netmask 0xffffff00 broadcast 192.168.10.255
        media: Ethernet autoselect (10Gbase-T <full-duplex>)
        status: active
        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>

However when I configure those interfaces in different VNET jails, there
is no network connectivity:

ping: sendto: Host is down

Same network config works OK if I simply pass ix0 and ix1 to jails,
without SR-IOV virtual interfaces.

The hardware has a very old BIOS and there are no SR-IOV settings to
enable or disable. However I thought if the BIOS did not support it
then the ix(4) driver would not be able to allocate ixv* interfaces and
I would not be able to set IP addresses on them.

Could anyone confirm if they had any luck configuring this with Intel
X520? And was this with the native ix(4) driver or did you have to
download latest Intel driver sources and build and use those instead?

Thanks.