Chapter 12. PCI Device Assignment

Procedure 12.3. Assigning a PCI device to a guest virtual machine with virsh

1. Identify the device

   First, identify the PCI device designated for device assignment to the virtual machine. Use the lspci command to list the available PCI devices. You can refine the output of lspci with grep.
   This example uses the Ethernet controller highlighted in the following output:

   # lspci | grep Ethernet
   00:19.0 Ethernet controller: Intel Corporation 82567LM-2 Gigabit Network Connection
   01:00.0 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01)
   01:00.1 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01)

   This Ethernet controller is shown with the short identifier 00:19.0. We need to find out the full identifier used by virsh in order to assign this PCI device to a virtual machine.
   To do so, combine the virsh nodedev-list command with the grep command to list all devices of a particular type (pci) that are attached to the host machine. Then look at the output for the string that maps to the short identifier of the device you wish to use.
   This example highlights the string that maps to the Ethernet controller with the short identifier 00:19.0. Note that the : and . characters are replaced with underscores in the full identifier.

   # virsh nodedev-list --cap pci
   pci_0000_00_00_0
   pci_0000_00_01_0
   pci_0000_00_03_0
   pci_0000_00_07_0
   pci_0000_00_10_0
   pci_0000_00_10_1
   pci_0000_00_14_0
   pci_0000_00_14_1
   pci_0000_00_14_2
   pci_0000_00_14_3
   pci_0000_00_19_0
   pci_0000_00_1a_0
   pci_0000_00_1a_1
   pci_0000_00_1a_2
   pci_0000_00_1a_7
   pci_0000_00_1b_0
   pci_0000_00_1c_0
   pci_0000_00_1c_1
   pci_0000_00_1c_4
   pci_0000_00_1d_0
   pci_0000_00_1d_1
   pci_0000_00_1d_2
   pci_0000_00_1d_7
   pci_0000_00_1e_0
   pci_0000_00_1f_0
   pci_0000_00_1f_2
   pci_0000_00_1f_3
   pci_0000_01_00_0
   pci_0000_01_00_1
   pci_0000_02_00_0
   pci_0000_02_00_1
   pci_0000_06_00_0
   pci_0000_07_02_0
   pci_0000_07_03_0

   Record the PCI device number that maps to the device you want to use; this is required in other steps.

2. Review device information

   Information on the domain, bus, and function are available from output of the virsh nodedev-dumpxml command:

   virsh nodedev-dumpxml pci_0000_00_19_0
   <device>
     <name>pci_0000_00_19_0</name>
     <parent>computer</parent>
     <driver>
       <name>e1000e</name>
     </driver>
     <capability type='pci'>
       <domain>0</domain>
       <bus>0</bus>
       <slot>25</slot>
       <function>0</function>
       <product id='0x1502'>82579LM Gigabit Network Connection</product>
       <vendor id='0x8086'>Intel Corporation</vendor>
       <capability type='virt_functions'>
       </capability>
     </capability>
   </device>

3. Determine required configuration details

   Refer to the output from the virsh nodedev-dumpxml pci_0000_00_19_0 command for the values required for the configuration file.
   Optionally, convert slot and function values to hexadecimal values (from decimal) to get the PCI bus addresses. Append "0x" to the beginning of the output to tell the computer that the value is a hexadecimal number.
   The example device has the following values: bus = 0, slot = 25 and function = 0. The decimal configuration uses those three values:

   bus='0'
   slot='25'
   function='0'

   If you want to convert to hexadecimal values, you can use the printf utility to convert from decimal values, as shown in the following example:

   $ printf %x 0
   0
   $ printf %x 25
   19
   $ printf %x 0
   0

   The example device would use the following hexadecimal values in the configuration file:

   bus='0x0'
   slot='0x19'
   function='0x0'

4. Add configuration details

   Run virsh edit, specifying the virtual machine name, and add a device entry in the <source> section to assign the PCI device to the guest virtual machine.

   # virsh edit guest1-rhel6-64
   <hostdev mode='subsystem' type='pci' managed='yes'>
     <source>
        <address domain='0x0' bus='0x0' slot='0x19' function='0x0'/>
     </source>
   </hostdev>

   Alternately, run virsh attach-device, specifying the virtual machine name and the guest's XML file:

   virsh attach-device guest1-rhel6-64 file.xml

5. Allow device management

   Set an SELinux boolean to allow the management of the PCI device from the virtual machine:

   # setsebool -P virt_use_sysfs 1

6. Start the virtual machine

   # virsh start guest1-rhel6-64