Installation guide

In this update, support for pselect() and ppoll() system calls has been added to the kernel.
6. Virtualization
This section contains information about updates made to Red Hat Enterprise Linux suite of Virtualization
tools.
6.1. Feature Updates
The blktap (blocktap) userspace toolkit has been updated, providing the functionality to monitor the
transfer statistics of blktap backed virtualized guests.
Support was added for the Intel Extended Page T able (EPT) feature, improving performance of fully
virtualized guests on hardware that supports EPT.
e1000 network device emulation for guests has been added in this update, supporting only
Windows 2003 guests on the ia64 architecture. To use e1000 emulation, the xm command must be
used.
Drivers for virtio, the platform for I/O virtualization in KVM, has been backported to Red Hat
Enterprise Linux 5.3 from Linux Kernel 2.6.27. These drivers will enable KVM guests to achieve
higher levels of I/O performance. Various userspace components such as: anaconda, kudzu, lvm,
selinux and m kinitrd have also been updated to support virtio devices.
The native Linux kernel supports vmcoreinfo automatically, but, to setup kdump on dom0 domains,
the kernel-xen-debuginfo package was needed. With this release, the kernel and the
hypervisor have been modified and now support vmcoreinfo reading and writing kdump natively.
Users needing to use kdump for de-bugging or other investigations on dom0 domains can now do so
without installing the debuginfo or debuginfo-com m on packages.
Fully virtualized Red Hat Enterprise Linux 5 guests encountered suboptimal performance when using
emulated disk and network devices. In this update, the kmod-xenpv package has been included to
simplify the use of paravirtualized disks and networks in fully virtualized guests.
Using these drivers in fully virtualized guests can significantly improve the performance and
functionality of fully virtualized guests. Bug fixes made for netfront and block front drivers are
immediately realized and synchronized with the kernel package.
Guests now have the ability to utilize 2MB backing page memory tables, which can improve system
performance.
6.2. Resolved Issues
6.2.1. All Architectures
Shutting down a paravirtualized guest may have caused the dom0 to stop responding for a period of
time. Delays of several seconds were experienced on guests with large amounts of memory (ie 12GB
and above.) In this update, the virtualized kernel allows the shutdown of a large paravirtualized guest
to be pre-emptible, which resolves this issue.
crash was unable to read the relocation address of the hypervisor from a vmcore file. Consequently,
opening a Virtualized kernel vmcore file with crash would fail, resulting in the error:
crash: cannot resolve "idle_pg_table_4"
In this update, the hypervisor now saves the address correctly, which resolves this issue.
Previously, paravirtualized guests could only have a maximum of 16 disk devices. In this update, this
limit has been increased to a maximum of 256 disk devices.
6. Virtualization
25