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31 I40E/IXGBE/IGB Virtual Function Driver
32 ======================================
34 Supported Intel® Ethernet Controllers (see the *DPDK Release Notes* for details)
35 support the following modes of operation in a virtualized environment:
37 * **SR-IOV mode**: Involves direct assignment of part of the port resources to different guest operating systems
38 using the PCI-SIG Single Root I/O Virtualization (SR IOV) standard,
39 also known as "native mode" or "pass-through" mode.
40 In this chapter, this mode is referred to as IOV mode.
42 * **VMDq mode**: Involves central management of the networking resources by an IO Virtual Machine (IOVM) or
43 a Virtual Machine Monitor (VMM), also known as software switch acceleration mode.
44 In this chapter, this mode is referred to as the Next Generation VMDq mode.
46 SR-IOV Mode Utilization in a DPDK Environment
47 ---------------------------------------------
49 The DPDK uses the SR-IOV feature for hardware-based I/O sharing in IOV mode.
50 Therefore, it is possible to partition SR-IOV capability on Ethernet controller NIC resources logically and
51 expose them to a virtual machine as a separate PCI function called a "Virtual Function".
52 Refer to :numref:`figure_single_port_nic`.
54 Therefore, a NIC is logically distributed among multiple virtual machines (as shown in :numref:`figure_single_port_nic`),
55 while still having global data in common to share with the Physical Function and other Virtual Functions.
56 The DPDK fm10kvf, i40evf, igbvf or ixgbevf as a Poll Mode Driver (PMD) serves for the Intel® 82576 Gigabit Ethernet Controller,
57 Intel® Ethernet Controller I350 family, Intel® 82599 10 Gigabit Ethernet Controller NIC,
58 Intel® Fortville 10/40 Gigabit Ethernet Controller NIC's virtual PCI function, or PCIe host-interface of the Intel Ethernet Switch
60 Meanwhile the DPDK Poll Mode Driver (PMD) also supports "Physical Function" of such NIC's on the host.
62 The DPDK PF/VF Poll Mode Driver (PMD) supports the Layer 2 switch on Intel® 82576 Gigabit Ethernet Controller,
63 Intel® Ethernet Controller I350 family, Intel® 82599 10 Gigabit Ethernet Controller,
64 and Intel® Fortville 10/40 Gigabit Ethernet Controller NICs so that guest can choose it for inter virtual machine traffic in SR-IOV mode.
66 For more detail on SR-IOV, please refer to the following documents:
68 * `SR-IOV provides hardware based I/O sharing <http://www.intel.com/network/connectivity/solutions/vmdc.htm>`_
70 * `PCI-SIG-Single Root I/O Virtualization Support on IA
71 <http://www.intel.com/content/www/us/en/pci-express/pci-sig-single-root-io-virtualization-support-in-virtualization-technology-for-connectivity-paper.html>`_
73 * `Scalable I/O Virtualized Servers <http://www.intel.com/content/www/us/en/virtualization/server-virtualization/scalable-i-o-virtualized-servers-paper.html>`_
75 .. _figure_single_port_nic:
77 .. figure:: img/single_port_nic.*
79 Virtualization for a Single Port NIC in SR-IOV Mode
82 Physical and Virtual Function Infrastructure
83 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
85 The following describes the Physical Function and Virtual Functions infrastructure for the supported Ethernet Controller NICs.
87 Virtual Functions operate under the respective Physical Function on the same NIC Port and therefore have no access
88 to the global NIC resources that are shared between other functions for the same NIC port.
90 A Virtual Function has basic access to the queue resources and control structures of the queues assigned to it.
91 For global resource access, a Virtual Function has to send a request to the Physical Function for that port,
92 and the Physical Function operates on the global resources on behalf of the Virtual Function.
93 For this out-of-band communication, an SR-IOV enabled NIC provides a memory buffer for each Virtual Function,
94 which is called a "Mailbox".
96 The PCIE host-interface of Intel Ethernet Switch FM10000 Series VF infrastructure
97 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
99 In a virtualized environment, the programmer can enable a maximum of *64 Virtual Functions (VF)*
100 globally per PCIE host-interface of the Intel Ethernet Switch FM10000 Series device.
101 Each VF can have a maximum of 16 queue pairs.
102 The Physical Function in host could be only configured by the Linux* fm10k driver
103 (in the case of the Linux Kernel-based Virtual Machine [KVM]), DPDK PMD PF driver doesn't support it yet.
107 * Using Linux* fm10k driver:
109 .. code-block:: console
111 rmmod fm10k (To remove the fm10k module)
112 insmod fm0k.ko max_vfs=2,2 (To enable two Virtual Functions per port)
114 Virtual Function enumeration is performed in the following sequence by the Linux* pci driver for a dual-port NIC.
115 When you enable the four Virtual Functions with the above command, the four enabled functions have a Function#
116 represented by (Bus#, Device#, Function#) in sequence starting from 0 to 3.
119 * Virtual Functions 0 and 2 belong to Physical Function 0
121 * Virtual Functions 1 and 3 belong to Physical Function 1
125 The above is an important consideration to take into account when targeting specific packets to a selected port.
127 Intel® Fortville 10/40 Gigabit Ethernet Controller VF Infrastructure
128 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
130 In a virtualized environment, the programmer can enable a maximum of *128 Virtual Functions (VF)*
131 globally per Intel® Fortville 10/40 Gigabit Ethernet Controller NIC device.
132 Each VF can have a maximum of 16 queue pairs.
133 The Physical Function in host could be either configured by the Linux* i40e driver
134 (in the case of the Linux Kernel-based Virtual Machine [KVM]) or by DPDK PMD PF driver.
135 When using both DPDK PMD PF/VF drivers, the whole NIC will be taken over by DPDK based application.
139 * Using Linux* i40e driver:
141 .. code-block:: console
143 rmmod i40e (To remove the i40e module)
144 insmod i40e.ko max_vfs=2,2 (To enable two Virtual Functions per port)
146 * Using the DPDK PMD PF i40e driver:
148 Kernel Params: iommu=pt, intel_iommu=on
150 .. code-block:: console
154 ./dpdk-devbind.py -b igb_uio bb:ss.f
155 echo 2 > /sys/bus/pci/devices/0000\:bb\:ss.f/max_vfs (To enable two VFs on a specific PCI device)
157 Launch the DPDK testpmd/example or your own host daemon application using the DPDK PMD library.
159 * Using the DPDK PMD PF ixgbe driver to enable VF RSS:
161 Same steps as above to install the modules of uio, igb_uio, specify max_vfs for PCI device, and
162 launch the DPDK testpmd/example or your own host daemon application using the DPDK PMD library.
164 The available queue number(at most 4) per VF depends on the total number of pool, which is
165 determined by the max number of VF at PF initialization stage and the number of queue specified
168 * If the max number of VF is set in the range of 1 to 32:
170 If the number of rxq is specified as 4(e.g. '--rxq 4' in testpmd), then there are totally 32
171 pools(ETH_32_POOLS), and each VF could have 4 or less(e.g. 2) queues;
173 If the number of rxq is specified as 2(e.g. '--rxq 2' in testpmd), then there are totally 32
174 pools(ETH_32_POOLS), and each VF could have 2 queues;
176 * If the max number of VF is in the range of 33 to 64:
178 If the number of rxq is 4 ('--rxq 4' in testpmd), then error message is expected as rxq is not
179 correct at this case;
181 If the number of rxq is 2 ('--rxq 2' in testpmd), then there is totally 64 pools(ETH_64_POOLS),
182 and each VF have 2 queues;
184 On host, to enable VF RSS functionality, rx mq mode should be set as ETH_MQ_RX_VMDQ_RSS
185 or ETH_MQ_RX_RSS mode, and SRIOV mode should be activated(max_vfs >= 1).
186 It also needs config VF RSS information like hash function, RSS key, RSS key length.
188 .. code-block:: console
190 testpmd -l 0-15 -n 4 -- --coremask=<core-mask> --rxq=4 --txq=4 -i
192 .. Note: The preferred option is -c XX or -l n-n,n instead of a coremask value. The --coremask option
193 is a feature of the application and not DPDK EAL options.
195 The limitation for VF RSS on Intel® 82599 10 Gigabit Ethernet Controller is:
196 The hash and key are shared among PF and all VF, the RETA table with 128 entries is also shared
197 among PF and all VF; So it could not to provide a method to query the hash and reta content per
198 VF on guest, while, if possible, please query them on host(PF) for the shared RETA information.
200 Virtual Function enumeration is performed in the following sequence by the Linux* pci driver for a dual-port NIC.
201 When you enable the four Virtual Functions with the above command, the four enabled functions have a Function#
202 represented by (Bus#, Device#, Function#) in sequence starting from 0 to 3.
205 * Virtual Functions 0 and 2 belong to Physical Function 0
207 * Virtual Functions 1 and 3 belong to Physical Function 1
211 The above is an important consideration to take into account when targeting specific packets to a selected port.
213 Intel® 82599 10 Gigabit Ethernet Controller VF Infrastructure
214 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
216 The programmer can enable a maximum of *63 Virtual Functions* and there must be *one Physical Function* per Intel® 82599
217 10 Gigabit Ethernet Controller NIC port.
218 The reason for this is that the device allows for a maximum of 128 queues per port and a virtual/physical function has to
219 have at least one queue pair (RX/TX).
220 The current implementation of the DPDK ixgbevf driver supports a single queue pair (RX/TX) per Virtual Function.
221 The Physical Function in host could be either configured by the Linux* ixgbe driver
222 (in the case of the Linux Kernel-based Virtual Machine [KVM]) or by DPDK PMD PF driver.
223 When using both DPDK PMD PF/VF drivers, the whole NIC will be taken over by DPDK based application.
227 * Using Linux* ixgbe driver:
229 .. code-block:: console
231 rmmod ixgbe (To remove the ixgbe module)
232 insmod ixgbe max_vfs=2,2 (To enable two Virtual Functions per port)
234 * Using the DPDK PMD PF ixgbe driver:
236 Kernel Params: iommu=pt, intel_iommu=on
238 .. code-block:: console
242 ./dpdk-devbind.py -b igb_uio bb:ss.f
243 echo 2 > /sys/bus/pci/devices/0000\:bb\:ss.f/max_vfs (To enable two VFs on a specific PCI device)
245 Launch the DPDK testpmd/example or your own host daemon application using the DPDK PMD library.
247 Virtual Function enumeration is performed in the following sequence by the Linux* pci driver for a dual-port NIC.
248 When you enable the four Virtual Functions with the above command, the four enabled functions have a Function#
249 represented by (Bus#, Device#, Function#) in sequence starting from 0 to 3.
252 * Virtual Functions 0 and 2 belong to Physical Function 0
254 * Virtual Functions 1 and 3 belong to Physical Function 1
258 The above is an important consideration to take into account when targeting specific packets to a selected port.
260 Intel® 82576 Gigabit Ethernet Controller and Intel® Ethernet Controller I350 Family VF Infrastructure
261 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
263 In a virtualized environment, an Intel® 82576 Gigabit Ethernet Controller serves up to eight virtual machines (VMs).
264 The controller has 16 TX and 16 RX queues.
265 They are generally referred to (or thought of) as queue pairs (one TX and one RX queue).
266 This gives the controller 16 queue pairs.
268 A pool is a group of queue pairs for assignment to the same VF, used for transmit and receive operations.
269 The controller has eight pools, with each pool containing two queue pairs, that is, two TX and two RX queues assigned to each VF.
271 In a virtualized environment, an Intel® Ethernet Controller I350 family device serves up to eight virtual machines (VMs) per port.
272 The eight queues can be accessed by eight different VMs if configured correctly (the i350 has 4x1GbE ports each with 8T X and 8 RX queues),
273 that means, one Transmit and one Receive queue assigned to each VF.
277 * Using Linux* igb driver:
279 .. code-block:: console
281 rmmod igb (To remove the igb module)
282 insmod igb max_vfs=2,2 (To enable two Virtual Functions per port)
284 * Using DPDK PMD PF igb driver:
286 Kernel Params: iommu=pt, intel_iommu=on modprobe uio
288 .. code-block:: console
291 ./dpdk-devbind.py -b igb_uio bb:ss.f
292 echo 2 > /sys/bus/pci/devices/0000\:bb\:ss.f/max_vfs (To enable two VFs on a specific pci device)
294 Launch DPDK testpmd/example or your own host daemon application using the DPDK PMD library.
296 Virtual Function enumeration is performed in the following sequence by the Linux* pci driver for a four-port NIC.
297 When you enable the four Virtual Functions with the above command, the four enabled functions have a Function#
298 represented by (Bus#, Device#, Function#) in sequence, starting from 0 to 7.
301 * Virtual Functions 0 and 4 belong to Physical Function 0
303 * Virtual Functions 1 and 5 belong to Physical Function 1
305 * Virtual Functions 2 and 6 belong to Physical Function 2
307 * Virtual Functions 3 and 7 belong to Physical Function 3
311 The above is an important consideration to take into account when targeting specific packets to a selected port.
313 Validated Hypervisors
314 ~~~~~~~~~~~~~~~~~~~~~
316 The validated hypervisor is:
318 * KVM (Kernel Virtual Machine) with Qemu, version 0.14.0
320 However, the hypervisor is bypassed to configure the Virtual Function devices using the Mailbox interface,
321 the solution is hypervisor-agnostic.
322 Xen* and VMware* (when SR- IOV is supported) will also be able to support the DPDK with Virtual Function driver support.
324 Expected Guest Operating System in Virtual Machine
325 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
327 The expected guest operating systems in a virtualized environment are:
329 * Fedora* 14 (64-bit)
331 * Ubuntu* 10.04 (64-bit)
333 For supported kernel versions, refer to the *DPDK Release Notes*.
335 Setting Up a KVM Virtual Machine Monitor
336 ----------------------------------------
338 The following describes a target environment:
340 * Host Operating System: Fedora 14
342 * Hypervisor: KVM (Kernel Virtual Machine) with Qemu version 0.14.0
344 * Guest Operating System: Fedora 14
346 * Linux Kernel Version: Refer to the *DPDK Getting Started Guide*
348 * Target Applications: l2fwd, l3fwd-vf
350 The setup procedure is as follows:
352 #. Before booting the Host OS, open **BIOS setup** and enable **Intel® VT features**.
354 #. While booting the Host OS kernel, pass the intel_iommu=on kernel command line argument using GRUB.
355 When using DPDK PF driver on host, pass the iommu=pt kernel command line argument in GRUB.
357 #. Download qemu-kvm-0.14.0 from
358 `http://sourceforge.net/projects/kvm/files/qemu-kvm/ <http://sourceforge.net/projects/kvm/files/qemu-kvm/>`_
359 and install it in the Host OS using the following steps:
361 When using a recent kernel (2.6.25+) with kvm modules included:
363 .. code-block:: console
365 tar xzf qemu-kvm-release.tar.gz
367 ./configure --prefix=/usr/local/kvm
370 sudo /sbin/modprobe kvm-intel
372 When using an older kernel, or a kernel from a distribution without the kvm modules,
373 you must download (from the same link), compile and install the modules yourself:
375 .. code-block:: console
377 tar xjf kvm-kmod-release.tar.bz2
382 sudo /sbin/modprobe kvm-intel
384 qemu-kvm installs in the /usr/local/bin directory.
386 For more details about KVM configuration and usage, please refer to:
388 `http://www.linux-kvm.org/page/HOWTO1 <http://www.linux-kvm.org/page/HOWTO1>`_.
390 #. Create a Virtual Machine and install Fedora 14 on the Virtual Machine.
391 This is referred to as the Guest Operating System (Guest OS).
393 #. Download and install the latest ixgbe driver from:
395 `http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=14687 <http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=14687>`_
399 When using Linux kernel ixgbe driver, unload the Linux ixgbe driver and reload it with the max_vfs=2,2 argument:
401 .. code-block:: console
404 modprobe ixgbe max_vfs=2,2
406 When using DPDK PMD PF driver, insert DPDK kernel module igb_uio and set the number of VF by sysfs max_vfs:
408 .. code-block:: console
412 ./dpdk-devbind.py -b igb_uio 02:00.0 02:00.1 0e:00.0 0e:00.1
413 echo 2 > /sys/bus/pci/devices/0000\:02\:00.0/max_vfs
414 echo 2 > /sys/bus/pci/devices/0000\:02\:00.1/max_vfs
415 echo 2 > /sys/bus/pci/devices/0000\:0e\:00.0/max_vfs
416 echo 2 > /sys/bus/pci/devices/0000\:0e\:00.1/max_vfs
420 You need to explicitly specify number of vfs for each port, for example,
421 in the command above, it creates two vfs for the first two ixgbe ports.
423 Let say we have a machine with four physical ixgbe ports:
434 The command above creates two vfs for device 0000:02:00.0:
436 .. code-block:: console
438 ls -alrt /sys/bus/pci/devices/0000\:02\:00.0/virt*
439 lrwxrwxrwx. 1 root root 0 Apr 13 05:40 /sys/bus/pci/devices/0000:02:00.0/virtfn1 -> ../0000:02:10.2
440 lrwxrwxrwx. 1 root root 0 Apr 13 05:40 /sys/bus/pci/devices/0000:02:00.0/virtfn0 -> ../0000:02:10.0
442 It also creates two vfs for device 0000:02:00.1:
444 .. code-block:: console
446 ls -alrt /sys/bus/pci/devices/0000\:02\:00.1/virt*
447 lrwxrwxrwx. 1 root root 0 Apr 13 05:51 /sys/bus/pci/devices/0000:02:00.1/virtfn1 -> ../0000:02:10.3
448 lrwxrwxrwx. 1 root root 0 Apr 13 05:51 /sys/bus/pci/devices/0000:02:00.1/virtfn0 -> ../0000:02:10.1
450 #. List the PCI devices connected and notice that the Host OS shows two Physical Functions (traditional ports)
451 and four Virtual Functions (two for each port).
452 This is the result of the previous step.
454 #. Insert the pci_stub module to hold the PCI devices that are freed from the default driver using the following command
455 (see http://www.linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM Section 4 for more information):
457 .. code-block:: console
459 sudo /sbin/modprobe pci-stub
461 Unbind the default driver from the PCI devices representing the Virtual Functions.
462 A script to perform this action is as follows:
464 .. code-block:: console
466 echo "8086 10ed" > /sys/bus/pci/drivers/pci-stub/new_id
467 echo 0000:08:10.0 > /sys/bus/pci/devices/0000:08:10.0/driver/unbind
468 echo 0000:08:10.0 > /sys/bus/pci/drivers/pci-stub/bind
470 where, 0000:08:10.0 belongs to the Virtual Function visible in the Host OS.
472 #. Now, start the Virtual Machine by running the following command:
474 .. code-block:: console
476 /usr/local/kvm/bin/qemu-system-x86_64 -m 4096 -smp 4 -boot c -hda lucid.qcow2 -device pci-assign,host=08:10.0
480 — -m = memory to assign
482 — -smp = number of smp cores
484 — -boot = boot option
486 — -hda = virtual disk image
488 — -device = device to attach
492 — The pci-assign,host=08:10.0 value indicates that you want to attach a PCI device
493 to a Virtual Machine and the respective (Bus:Device.Function)
494 numbers should be passed for the Virtual Function to be attached.
496 — qemu-kvm-0.14.0 allows a maximum of four PCI devices assigned to a VM,
497 but this is qemu-kvm version dependent since qemu-kvm-0.14.1 allows a maximum of five PCI devices.
499 — qemu-system-x86_64 also has a -cpu command line option that is used to select the cpu_model
500 to emulate in a Virtual Machine. Therefore, it can be used as:
502 .. code-block:: console
504 /usr/local/kvm/bin/qemu-system-x86_64 -cpu ?
506 (to list all available cpu_models)
508 /usr/local/kvm/bin/qemu-system-x86_64 -m 4096 -cpu host -smp 4 -boot c -hda lucid.qcow2 -device pci-assign,host=08:10.0
510 (to use the same cpu_model equivalent to the host cpu)
512 For more information, please refer to: `http://wiki.qemu.org/Features/CPUModels <http://wiki.qemu.org/Features/CPUModels>`_.
514 #. Install and run DPDK host app to take over the Physical Function. Eg.
516 .. code-block:: console
518 make install T=x86_64-native-linuxapp-gcc
519 ./x86_64-native-linuxapp-gcc/app/testpmd -l 0-3 -n 4 -- -i
521 #. Finally, access the Guest OS using vncviewer with the localhost:5900 port and check the lspci command output in the Guest OS.
522 The virtual functions will be listed as available for use.
524 #. Configure and install the DPDK with an x86_64-native-linuxapp-gcc configuration on the Guest OS as normal,
525 that is, there is no change to the normal installation procedure.
527 .. code-block:: console
529 make config T=x86_64-native-linuxapp-gcc O=x86_64-native-linuxapp-gcc
530 cd x86_64-native-linuxapp-gcc
535 If you are unable to compile the DPDK and you are getting "error: CPU you selected does not support x86-64 instruction set",
536 power off the Guest OS and start the virtual machine with the correct -cpu option in the qemu- system-x86_64 command as shown in step 9.
537 You must select the best x86_64 cpu_model to emulate or you can select host option if available.
541 Run the DPDK l2fwd sample application in the Guest OS with Hugepages enabled.
542 For the expected benchmark performance, you must pin the cores from the Guest OS to the Host OS (taskset can be used to do this) and
543 you must also look at the PCI Bus layout on the board to ensure you are not running the traffic over the QPI Interface.
547 * The Virtual Machine Manager (the Fedora package name is virt-manager) is a utility for virtual machine management
548 that can also be used to create, start, stop and delete virtual machines.
549 If this option is used, step 2 and 6 in the instructions provided will be different.
551 * virsh, a command line utility for virtual machine management,
552 can also be used to bind and unbind devices to a virtual machine in Ubuntu.
553 If this option is used, step 6 in the instructions provided will be different.
555 * The Virtual Machine Monitor (see :numref:`figure_perf_benchmark`) is equivalent to a Host OS with KVM installed as described in the instructions.
557 .. _figure_perf_benchmark:
559 .. figure:: img/perf_benchmark.*
561 Performance Benchmark Setup
564 DPDK SR-IOV PMD PF/VF Driver Usage Model
565 ----------------------------------------
567 Fast Host-based Packet Processing
568 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
570 Software Defined Network (SDN) trends are demanding fast host-based packet handling.
571 In a virtualization environment,
572 the DPDK VF PMD driver performs the same throughput result as a non-VT native environment.
574 With such host instance fast packet processing, lots of services such as filtering, QoS,
575 DPI can be offloaded on the host fast path.
577 :numref:`figure_fast_pkt_proc` shows the scenario where some VMs directly communicate externally via a VFs,
578 while others connect to a virtual switch and share the same uplink bandwidth.
580 .. _figure_fast_pkt_proc:
582 .. figure:: img/fast_pkt_proc.*
584 Fast Host-based Packet Processing
587 SR-IOV (PF/VF) Approach for Inter-VM Communication
588 --------------------------------------------------
590 Inter-VM data communication is one of the traffic bottle necks in virtualization platforms.
591 SR-IOV device assignment helps a VM to attach the real device, taking advantage of the bridge in the NIC.
592 So VF-to-VF traffic within the same physical port (VM0<->VM1) have hardware acceleration.
593 However, when VF crosses physical ports (VM0<->VM2), there is no such hardware bridge.
594 In this case, the DPDK PMD PF driver provides host forwarding between such VMs.
596 :numref:`figure_inter_vm_comms` shows an example.
597 In this case an update of the MAC address lookup tables in both the NIC and host DPDK application is required.
599 In the NIC, writing the destination of a MAC address belongs to another cross device VM to the PF specific pool.
600 So when a packet comes in, its destination MAC address will match and forward to the host DPDK PMD application.
602 In the host DPDK application, the behavior is similar to L2 forwarding,
603 that is, the packet is forwarded to the correct PF pool.
604 The SR-IOV NIC switch forwards the packet to a specific VM according to the MAC destination address
605 which belongs to the destination VF on the VM.
607 .. _figure_inter_vm_comms:
609 .. figure:: img/inter_vm_comms.*
611 Inter-VM Communication