Installation guide

# virsh nodedev-reattach pci_8086_3a6c
15.5. PCI passt hrough for para-virt ualized Xen guest s on Red Hat
Ent erprise Linux
PCI passthrough is used to allow a Xen guest exclusive access to a PCI device, rather than sharing
with other guests or with dom0. PCI passthrough for para-virtualized Xen guests is supported on all
Red Hat Enterprise Linux 5 systems, however PCI passthrough with fully virtualized guests is only
supported on Red Hat Enterprise Linux 5.4 and newer.
Warning
PCI passthrough to para-virtualized guests is considered insecure and is not supported for
Red Hat Enterprise Linux 6 guests.
Limit at ion s o f Xen PCI p asst h ro u g h:
Any guest using PCI passthrough will no longer be available for save, restore, or migration
capabilities, as it will be tied to a particular non-virtualized hardware configuration.
A guest which has access to a non-virtualized PCI device via PCI passthrough also has the potential
to access the DMA address space of dom0, which is a potential security concern.
To link a PCI device to a guest the device must first be hidden from the host. If the host is using the
device, the device cannot be assigned to the guest.
Pro ced u re 15.3. Examp le: at t ach in g a PC I device
1. Given a network device which uses the bnx2 driver and has a PCI id of 0000:09:00.0, the
following lines added to /etc/modprobe.conf hides the device from dom0. Either the bnx2
module must be reloaded or the host must be restarted.
install bnx2 /sbin/modprobe pciback; /sbin/modprobe --first-time --ignore-
install bnx2
options pciback hide=(0000:09:00.0)
2. Multiple PCI identifiers can be added to /etc/modprobe.conf to hide multiple devices.
options pciback hide=(0000:09:00.0)(0000:0a:04.1)
3. Use one of the following methods to add the passed-through device to the guest's
configuration file:
virsh (Section 15.1, “ Adding a PCI device with virsh” - Step 5);
virt-manager (Section 15.2, “ Adding a PCI device with virt-manager” ); or
virt-install (Section 15.3, “ PCI passthrough with virt-install” )
Red Hat En t erp rise Lin ux 5 Virt ualizat ion Guid e
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