With the release of an OFED which supports SR-IOV on Infiniband HCAs it is now possible to use verbs from inside a VM. This VMM driver supports these Infiniband HCAs, and any other SR-IOV network device, in OpenNebula.

Demonstration Video: OpenNebula KVM SR-IOV Driver

1. This driver has been developed to support OpenNebula 4.x and KVM. The driver should be backwards compatible the OpenNebula 3.x.
2. SR-IOV capable hardware and software is required. Before using this driver SR-IOV must be functional on the VM host.
3. Libvirt must run as root. This is required for the hypervisor to attach the SR-IOV virtual function to the VM.
4. Any OpenNebula functions which rely on the “virsh save” command (stop, suspend and migrate) require the virtual functions to be hot plugged. This may cause unpredictable behaviour on the OS running in the VM. (More info)
5. A virtual bridge is required when using the driver in generic mode. The VM will attach interfaces to this bridge but the OS will not use them. They are only required to pass IP address information into the VM. The bridge does not require any external connectivity, it just needs to exist. (More info)
6. VF usage tracking is implemented in the /tmp file system. During a fatal host error the VF usage tracking might become out of sync with actual VF usage. You will have to manually recover. (More info)
7. A modified context script is required to decode the SR-IOV interface information inside the VM. An example is given for Infiniband.
8. The maximum number of VMs with SR-IOV interfaces that the host can support is limited by the number of VFs the root device exposes. Usually around 64.
9. To use this driver with Ethernet SR-IOV devices you will need to modify the VM context script and take into consideration MAC prefixes. (More info)
10. Network isolation with SR-IOV interfaces is only supported on Mellanox ConnectX-3 HCAs with OFED v2.0-3.0.0 and a patched version of the ovswitch VNM driver is required. (More info)
11. IPv6 has not been tested.

1. CentOS 6.4
2. Mellanox OFED 2.0-3.0.0
3. libvirt 0.10.2
4. OpenNebula 4.2

1. Download and extract SR-IOV KVM Driver v0.2 to a temporary location

2. As root execute install.sh and follow the on-screen instructions

3. Edit /etc/one/oned.conf and add:

  VM_MAD = [
      name       = "kvm_sriov",
      executable = "one_vmm_exec",
      arguments  = "-t 15 -r 0 kvm-sriov",
      default    = "vmm_exec/vmm_exec_kvm.conf",
      type       = "kvm" ]

4. Use this guide to extract the bus slot and function addresses for the virtual functions: Virtualization Host Configuration and Guest Installation Guide - SR_IOV - How SR_IOV_Libvirt Works

5. In the /var/lib/one/remotes/vmm/kvm-sriov/vf_maps directory create a file with the name of the VF's root device, e.g. “ib0”. In the file write the bus, slot and function for each VF you want the driver to use. The address must be in hexadecimal. Each line in the file represents a VF, the bus, slot and function addresses are separated by a single space character “ “. There must be no additional text, spaces or lines in the table.

Example, four virtual functions:

/var/lib/one/remotes/vmm/kvm-sriov/vf_maps/ib0:

  0x07 0x00 0x01
  0x07 0x00 0x02
  0x07 0x00 0x03
  0x07 0x00 0x04

6. If using the driver in “mlnx_ofed2” mode you need to specify the device and port number of the interface. To find the device ID execute:

  ls /sys/class/infiniband

You will see a list of Infiniband devices “mlx4_<x>”. The device ID is the <x>. To find the port ID execute:

  ls /sys/class/infiniband/mlx4_<x>/ports

You will see a list of numbers representing the ports available on the device.

Each interface which you have created a map for needs an additional file called “<map_name>_ofed”, eg. “ib0_ofed”. The file contains two lines specifying its associated device and port.

Example,

/var/lib/one/remotes/vmm/kvm-sriov/vf_maps/ib0_ofed:

 device 0
 port   1

7. On VM hosts using this driver edit /etc/libvirt/qemu.conf and change the user and group to “root” then restart libvirtd.

8. On the head node restart OpenNebula.

9. Create a virtual network in OpenNebula. The “Bridge” field must contain “sriov_” prepended to the name of the file that contains the VF mapings, e.g. “sriov_ib0”

10. Update the contextualisation scripts for the VMs with the code provided here.

11. Create hosts to use the “kvm_sriov” driver.

The “save” command saves the state of the VM's memory to the host's disk. This operation fails when a VM contains an SR-IOV device because it is passed through the hypervisor and not defined by it. As a result the device's memory state cannot be read, causing the save operation to fail.

To work around this issue the kvm-sriov driver will hot remove SR-IOV interfaces before executing the “save” command, and hot attach SR-IOV devices after executing the “restore” command.

This driver also supports live migration. Before migrating a VM the driver will attempt to acquire VF locks at the destination. If the migration fails the driver will attempt to reattach the devices at the source.

The dummy bridge and interfaces are only required if you operate the driver in the “generic” mode. In this mode the dummy interfaces will be attached to the dummy bridge to pass IP address into the VM.

If you operate the driver in the “mlnx_ofed2” mode it will encode IP address into the VM's Infiniband GUID. The contextualisation scripts must be modified to support reading IP address from GUIDs. An example is provided below.

Libvirt does provide a built-in method for tracking VF usage but it does not support the Mellanox OFED 2 drivers. As a result I had to create my own usage tracking mechanism. If you are using this driver with an SR-IOV card which supports VF assignment from a pool then you can use the instructions found below to update the scripts: http://wiki.libvirt.org/page/Networking#Assignment_from_a_pool_of_SRIOV_VFs_in_a_libvirt_.3Cnetwork.3E_definition

The independent tracking mechanism provided with this driver creates a vf_interfaces directory in the host's /tmp directory. Inside the vf_interfaces directory a directory will be created for each SR-IOV root device. Inside the root device's directory files will be created to indicate that a VF is in use. For example, if the first, third and fourth VF are in use you see:

/tmp/vf_interfaces/ib0:

  0
  2
  3

This driver will always put the libvirt interfaces used for passing IP information at the end of the devices list. This means that if you create a VM with a mix of SR-IOV and libvirt interfaces they will be labeled consecutively and in the same order as displayed in OpenNebula.

Also, you must ensure that Ethernet VFs do not contain either the OpenNebula default MAC prefix or the one specified for identifying SR-IOV devices. To ensure this write a script that checks and sets the MAC addresses of the root device's VFs once the host has booted.

The context script will need to be updated to support the Ethernet devices, however the changes are minimal and simple.

Enabling huge pages on KVM virtual machines will greatly improve memory performance. To enable huge pages on your VM hosts follow these instructions: http://www.linux-kvm.com/content/get-performance-boost-backing-your-kvm-guest-hugetlbfs

Huge page backed VMs will be enabled if “HPC_MODE” is set “on”.

This driver supports network isolation on all virtual interfaces through the standard OpenNebula VNM drivers. Isolation on SR-IOV devices is only supported on Mellanox ConnectX-3 HCAs. The Infiniband isolation is implemented through a modified version of the “ovswitch” driver which ships with OpenNebula.

To use Infiniband isolation the host and network must be set to use the Open vSwitch driver. The IB Pkey is set in the VLAN field when creating a network. Note, the Pkey must be specified in decimal. It will be converted into hexadecimal and a full key will be generated from it.

The driver assumes the IB fabric has been correctly configured with the requested partitions. If during deployment the requested pkey is not found the virtual function will be blocked. If you do not specify a pkey the default partition will be used.

• SR-IOV KVM Driver v0.2

Edit the 00-network script (in our case: /srv/one-context.d/00-network). Update the gen_network_configuration() and gen_iface_conf() functions.

gen_iface_conf() {
  cat <<EOT
  DEVICE=$DEV
  BOOTPROTO=none
  ONBOOT=yes
  ####################
  # Update this      #
  ####################
  TYPE=$TYPE
  #-------------------
  NETMASK=$MASK
  IPADDR=$IP
  EOT
    if [ -n "$GATEWAY" ]; then
      echo "GATEWAY=$GATEWAY"
    fi
    echo ""
}

gen_network_configuration()
{
  IFACES=`get_interfaces`
  for i in $IFACES; do
      MAC=`get_mac $i`
      ###################################
      # Update this                     #
      ###################################
      ib_vf=$(echo "$MAC" | cut -c 1-2)
      ib_pos=$(echo "$MAC" | cut -c 5)
      if  [ "$ib_vf" == "AA" ]; then
        DEV="ib"$ib_pos
        UPCASE_DEV=`upcase $DEV`
        TYPE="Infiniband"
      else
        DEV=`get_dev $i`
        UPCASE_DEV=`upcase $DEV`
        TYPE="Ethernet"
      fi
      #-----------------------------------
      IP=$(get_ip)
      NETWORK=$(get_network)
      MASK=$(get_mask)
      GATEWAY=$(get_gateway)
      ####################################
      # Update this                      #
      ####################################
      if  [ "$ib_vf" == "AA" ]; then
        gen_iface_conf > /etc/sysconfig/network-scripts/ifcfg-ib$ib_pos
      else
        gen_iface_conf > /etc/sysconfig/network-scripts/ifcfg-${DEV}
      fi
      #-----------------------------------
  done
  ####################################################################################################
  # Add this                                                                                         #
  ####################################################################################################
  down_ifs=`ip addr | grep "mtu" | wc -l`
  position=0
  while [ $position -lt $down_ifs ]
  do
      position=$[$position + 1]
      is_ib=`ip addr | grep "mtu" -A 1 | grep link/ | sed "$position q;d" | grep infiniband | wc -l`
      if [ $is_ib -gt 0 ]; then
        DEV=`ip addr | grep "mtu" | sed "$position q;d" | awk '{print $2}' | cut -d ":" -f1`
        if [ ! -f /etc/sysconfig/network-scripts/ifcfg-${DEV} ]; then
          MAC=`ip addr | grep "mtu" -A 1 | grep link/ | sed "$position q;d" | awk '{print $2}' | rev | cut -c -17 | rev`
          UPCASE_DEV=`upcase $DEV`
          TYPE="Infiniband"
          IP=$(get_ip)
          NETWORK=$(get_network)
          MASK=$(get_mask)
          GATEWAY=$(get_gateway)
          gen_iface_conf > /etc/sysconfig/network-scripts/ifcfg-${DEV}
        fi
      fi
  done    
  #---------------------------------------------------------------------------------------------------
}

Take note of:

1. “$ib_vf” == “AA”. This means that the script is expecting AA as the MAC prefix for SR-IOV devices.
2. gen_iface_conf > /etc/sysconfig/network-scripts/ifcfg-ib$ib_pos. The ifcfg file is being generated for Infiniband.

Copyright 2013, CSIR Centre for High Performance Computing
Author: David Macleod

Licensed under the Apache License, Version 2.0 (the "License"); you may
not use this file except in compliance with the License. You may obtain
a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, 
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

• David Macleod
• dmacleod@csir.co.za

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