6.5.1

Table Of Contents
2 The VF forwards the request to the PF through a mailbox mechanism.
3 The PF driver checks the configuration request with the virtual switch (standard switch or host proxy
switch of a distributed switch).
4 The virtual switch verifies the configuration request against the policy on the port with which the VF
enabled virtual machine adapter is associated.
5 The PF driver configures the VF if the new settings are in compliance with the port policy of the virtual
machine adapter.
For example, if the VF driver tries to modify the MAC address, the address remains the same if MAC
address change is not allowed in the security policy for the port group or port. The guest operating
system might show that the change is successful but a log message indicates that the operation has
failed. As a result, the guest operating system and the virtual device save different MAC addresses.
The network interface in the guest operating system might not be able to acquire an IP address and
communicate. In this case, you have to reset the interface in the guest operating system to get the
latest MAC address from the virtual device and acquire an IP address.
vSphere and Virtual Function Interaction
Virtual functions (VFs) are lightweight PCIe functions that contain all the resources necessary for data
exchange but have a minimized set of configuration resources. Interaction between vSphere and VFs is
limited.
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The physical NIC must use MSI-X interrupts.
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VFs do not implement rate control in vSphere. Every VF can potentially use the entire bandwidth of a
physical link.
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When a VF device is configured as a passthrough device on a virtual machine, the standby and
hibernate functions for the virtual machine are not supported.
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The maximum number of VFs that you can create and the maximum number of VFs that you can use
for passthrough are different. The maximum number of VFs that you can instantiate depends on the
NIC capability and on the hardware configuration of the host. However, due to the limited number of
interrupt vectors available for passthrough devices, only a limited number of all instantiated VFs can
be used on an ESXi host.
The total number of interrupt vectors on each ESXi host can scale up to 4096 in the case of 32 CPUs.
When the host boots, devices on the host such as storage controllers, physical network adapters, and
USB controllers consume a subset of the 4096 vectors. If these devices require more than 1024
vectors, the maximum number of potentially supported VFs is reduced.
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The number of VFs that is supported on an Intel NIC might be different from the number that is
supported on an Emulex NIC. See the technical documentation from the NIC vendor.
vSphere Networking
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