5.33. xen

As of Red Hat Enterprise Linux 5.4, PCI devices connected to a single PCI-PCI bridge can no longer be assigned to different PV guests. If the old, unsafe behaviour is required, disable pci-dev-assign-strict-check in /etc/xen/xend-config.sxp. (BZ#508310)
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. (BZ#426861)
When running x86_64 Xen, it is recommended to set dom0-min-mem in /etc/xen/xend-config.sxp to a value of 1024 or higher. Lower values may cause the dom0 to run out of memory, resulting in poor performance or out-of-memory situations. (BZ#519492)
The Red Hat Enterprise Linux 3 kernel does not include SWIOTLB support. SWIOTLB support is required for Red Hat Enterprise Linux 3 guests to support more than 4GB of memory on AMD Opteron and Athlon-64 processors. Consequently, Red Hat Enterprise Linux 3 guests are limited to 4GB of memory on AMD processors. (BZ#504187)
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. (BZ#429154, BZ#429154)
The Hypervisor outputs messages regarding attempts by any guest to write to an MSR. Such messages contain the statement Domain attempted WRMSR. These messages can be safely ignored; furthermore, they are rate limited and should pose no performance risk. (BZ#477647)

The following note applies to x86_64 Architectures:

Installing Red Hat Enterprise Linux 3.9 on a fully virtualized guest may be extremely slow. In addition, booting up the guest after installation may result in hda: lost interrupt errors.
To avoid this bootup error, configure the guest to use the SMP kernel. (BZ#249521)