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Configuring VMDirectPath I/O pass-through devices on a VMware ESX or VMware ESXi host (1010789)


This article provides information on configuring VMDirectPath I/O direct PCI device connections for virtual machines running on Intel Weybridge and Stoakley platforms.


About VMDirectPath I/O pass-through devices

You can connect up to two passthrough (ESX 4.0) and up to four passthrough (ESX 4.1) devices to a virtual machine. When selecting the devices, keep in mind these restrictions:
  • Devices cannot be plugged in after a PCI Bridge.
  • Device must be behind a PCI Switch that supports ACS.
  • Devices cannot be plugged in after a non-ACS switch.

    For more information, see
    PCI Passthrough with PCIe devices behind a non-ACS switch in vSphere (1036811)

  • You cannot have two devices in two different contexts -- such as one used by VMkernel and one in pass-through -- using the same PCI slot. For example, the dual head NIC is dedicated to the VMkernel OR is available for pass-through. If you select one, the other is automatically selected as well. A dialog informs you why this occurred.
  • Do not enable pass-through on the USB controller which is booting from USB device or SD card.

    For more information, see Unable to disable USB controller for passthrough after it is enabled (2068645)

Configuring pass-through devices

To configure pass-through devices on an ESX/ESXi host:
  1. Select an ESX host from the Inventory of VMware vSphere Client.

    Note: If you have a chipset with VT-d, when you click Advanced Settings in vSphere Client, you can select the devices that are dedicated to the VMDirectPath I/O.

  2. In the Configuration tab, click Advanced SettingsThe Pass-through Configuration page lists all available pass-through devices.

    A green icon indicates that a device is enabled and active. An orange icon indicates that the state of the device has changed and the host must be rebooted before the device can be used.

  3. Click Edit.
  4. Select the devices and click OK.
  5. When the devices are selected, they are marked with an orange icon. Reboot for the change to take effect. After rebooting, the devices are marked with a green icon and are enabled.

    Note: The configuration changes are saved in the /etc/vmware/esx.conf file. The parent PCI bridge, and if two devices are under the same PCI bridge, only one entry is recorded. 

    The PCI slot number where the device was connected is 00:0b:0. It is recorded as:

    /device/000:11.0/owner = "passthru"

    11 is the decimal equivalent of the hexadecimal
To configure a PCI device on a virtual machine:
  1. From the Inventory in vSphere Client, right-click the virtual machine and choose Edit Settings.
  2. Click the Hardware tab.
  3. Click Add.
  4. Choose the PCI Device.
  5. Click Next.

    Note: When the device is assigned, the virtual machine must have a memory reservation for the full configured memory size.

Additional Information

For more information, see the Technical Note Configuration Examples and Troubleshooting for VMDirectPath.

There may be issues, with the HP host pass-trhough when using version 5.1 patch 2 and later. For more information, see HP Advisory c03835455.


up to two passthrough

See Also

Request a Product Feature

To request a new product feature or to provide feedback on a VMware product, please visit the Request a Product Feature page.


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