Product SiteDocumentation Site

2. Virtualization

Red Hat Enterprise Linux 5.5 delivers many updates to virtualization. Detailed notes on all the changes to virtualization components are available in the Technical Notes.


Management of KVM based virtual guests using Cluster Suite is now fully supported.


Red Hat Enterprise Linux 5.5 includes components providing functionality for the Simple Protocol for Independent Computing Environments (SPICE) remote display protocol. These components, are for use in conjunction with Red Hat Enterprise Virtualization products and are not guaranteed to have a stable ABI. The components will be updated to synchronize with functional requirements of Red Hat Enterprise Virtualization products. Migration to future releases may require manual operations on a per-system basis.
PCI passthrough improvements
PCI passthrough allows PCI devices to appear and behave as if they were physically attached to the guest operating system. KVM and Xen hypervisors both support attaching PCI devices on the host system to virtualized guests.
The AMD input/output memory management unit (IOMMU) kernel driver, which assists in PCI passthrough, has been updated. This update fixes an issue where system management requests were handled incorrectly. (BZ#531469)
Support for PCI passthrough using Intel VT-d extensions on the KVM hypervisor has been improved. Devices (either physical or virtual) can now be shutdown and unassigned from a guest during runtime, allowing the device to be reassigned to another guest. This reassignment can also be carried out live (BZ#516811). Additionally, 1:1 mapping performance has been improved (BZ#518103).


For detailed information on virtualization, the Virtualization Guide is the definitive guide for virtualization on Red Hat Enterprise Linux.
HugePages Support
New rules are available in libvirt to enable hugetlbfs (HugePages). When a system is configured with Hugepages, libvirt automatically allocates memory from hugetlbfs to back the virtual guest memory. When combined with extended page tables and nested page tables in hardware, significant performance improvements can be achieved by the guest. (BZ#518099)

Note: This documentation is provided {and copyrighted} by Red Hat®, Inc. and is released via the Open Publication License. The copyright holder has added the further requirement that Distribution of substantively modified versions of this document is prohibited without the explicit permission of the copyright holder. The CentOS project redistributes these original works (in their unmodified form) as a reference for CentOS-5 because CentOS-5 is built from publicly available, open source SRPMS. The documentation is unmodified to be compliant with upstream distribution policy. Neither CentOS-5 nor the CentOS Project are in any way affiliated with or sponsored by Red Hat®, Inc.