Passthrough devices provide the means to more efficiently use resources and improve performance in your environment. You can configure a passthrough PCI device on a virtual machine in the vSphere Client.

When using passthrough devices with a Linux kernel version 2.6.20 or earlier, avoid MSI and MSI-X modes because these modes have significant performance impact.


Verify that a passthrough networking device is configured on the host of the virtual machine. See Enable Passthrough for a Network Device on a Host.


  1. Locate the virtual machine in the vSphere Client.
    1. Select a data center, folder, cluster, resource pool, or host and click the VMs tab.
    2. Click Virtual Machines and click the virtual machine from the list.
  2. Power off the virtual machine.
  3. From the Actions menu, select Edit Settings.
  4. Select the Virtual Hardware tab in the dialog box displaying the settings.
  5. Expand the Memory section, and set the Limit to Unlimited.
  6. Click the Add new device button and under Other devices, select PCI Device.
    The New PCI device drop-down menu is added to the list in the Virtual Hardware tab.
  7. From the New PCI device drop-down menu select the passthrough device to use, and click OK.
  8. Power on the virtual machine.


Adding a DirectPath I/O device to a virtual machine sets memory reservation to the memory size of the virtual machine.