Installation guide

Release Notes

6.3. Known Issues

6.3.1. All Architectures

• Diskette drive media will not be accessible when using the virtualized kernel. To work around this,

use a USB-attached diskette drive instead.

Note that diskette drive media works well with other non-virtualized kernels.

• In live migrations of paravirtualized guests, time-dependent guest processes may function

improperly if the corresponding hosts' (dom0) times are not synchronized. Use NTP to synchronize

system times for all corresponding hosts before migration.

• Repeated live migration of paravirtualized guests between two hosts may cause one host to panic.

If a host is rebooted after migrating a guest out of the system and before migrating the same guest

back, the panic will not occur.

• Formatting a disk when running Windows 2008 or Windows Vista as a guest can crash when the

guest has been booted with multiple virtual CPUs. To work around this, boot the guest with a single

virtual CPU when formatting.

• Fully virtualized guests created through virt-manager may sometimes prevent the mouse from

moving freely throughout the screen. To work around this, use virt-manager to configure a USB

tablet device for the guest.

• The maximum CPUs must be restricted to less than 128 when on a 128 or greater CPU system. The

maximum that is supported at this time is 126. Use the maxcpus=126 hypervisor argument to limit

the Hypervisor to 126

• Fully virtualized guests cannot correct for time lost due to the domain being paused and unpaused.

Being able to correctly track the time across pause and unpause events is one of the advantages

of paravirtualized kernels. This issue is being addressed upstream with replaceable timers, so

fully virtualized guests will have paravirtualized timers. Currently, this code is under development

upstream and should be available in later versions of Red Hat Enterprise Linux.

• Repeated migration of paravirtualized guests may result in bad mpa messages on the dom0

console. In some cases, the hypervisor may also panic.

To prevent a hypervisor kernel panic, restart the migrated guests once the bad mpa messages

appear.

• When setting up interface bonding on dom0, the default network-bridge script may cause

bonded network interfaces to alternately switch between unavailable and available. This

occurrence is commonly known as flapping.

To prevent this, replace the standard network-script line in /etc/xen/xend-config.sxp

with the following line:

(network-script network-bridge-bonding netdev=bond0)

Doing so will disable the netloop device, which prevents Address Resolution Protocol (ARP)

monitoring from failing during the address transfer process.