X710-DA4 - SR-IOV not working correctly

Host OS: Ubuntu 16.04 LTS

Hypervisor: Xen 4.6.0

Kernel version: 4.4.0-22-generic

Driver version: i40e-1.5.18

NVM version: 5.02

Guest OS: Windows Server 2012 R2

Guest Driver version: 20.7.1

I'm trying to forward the ports of the card to a guest Windows VM.  An example of forwarding just one port:

# echo 1 > /sys/class/net/ens2f0/device/sriov_numvfs

# /sbin/ip link set ens2f0 vf 0 mac 02:00:00:00:00:00

# xl pci-assignable-add 02:02.0

Added to Xen VM .cfg:

pci = ['0000:02:02.0']

All of that works and the VM starts fine and sees the card.  Xen reports that it added it:

[26326.586765] i40e 0000:02:00.0 ens2f0: adding 68:05:ca:33:0a:59 vid=0

[26326.586774] i40e 0000:02:00.0 ens2f0: adding 68:05:ca:33:0a:59 vid=1

[26326.595995] i40e 0000:02:00.0: Allocating 1 VFs.

[26326.697778] pci 0000:02:02.0: [8086:154c] type 00 class 0x020000

[26326.697973] pci 0000:02:02.0: Max Payload Size set to 256 (was 128, max 2048)

[26329.893582] i40e 0000:02:00.0: Setting MAC 02:00:00:00:00:00 on VF 0

[26329.965339] i40e 0000:02:00.0: Reload the VF driver to make this change effective.

[26366.200750] pciback 0000:02:02.0: seizing device

[26366.200815] pciback 0000:02:02.0: enabling device (0000 -> 0002)

[26472.867101] xen_pciback: vpci: 0000:02:02.0: assign to virtual slot 0

[26472.867643] pciback 0000:02:02.0: registering for 4

I install the drivers and Windows 'see' the card.  The problem is the reported state goes into a cycle:

Connected @ 10GB

Connected @ 40GB

Disconnected

When this happens, in dmesg on the host:

[26624.137415] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26635.075640] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26645.903762] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26656.669642] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26667.904191] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26679.013381] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26689.966331] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26701.028906] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26712.372668] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26723.154159] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26733.935320] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26744.685130] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

[26756.075844] i40e 0000:02:00.0: VF 0 failed opcode 11, retval: -10

This same issue happens using the built in kernel i40e and also i40e-1.5.18. Am I doing something wrong?