RHBA-2011:0326 - Bug Fix Advisory

Topic

Updated xen packages that fix various bugs are now available for Red Hat
Enterprise Linux 5 Extended Update Support.

Description

Xen is a high-performance and secure open source virtualization framework.
Virtualization allows users to run guest operating systems in virtual machines
on top of a host operating system.

This update fixes the following bugs:

• With a large number of virtual block devices (VBDs) or virtual guests, looking

for duplicate devices could take a very long time and significantly increase
overall boot time. With this update, this procedure has been optimized not to
require XenStore, so that virtual guests now boot much faster. Additionally,
this update also ensures that the domain record counter contains a correct value
when a XenStore transaction is canceled. Note that when you add a network
interface controller (NIC) with an automatically generated MAC address, this
address is not verified. Avoid using a combination of hard-coded and
automatically assigned MAC addresses, as this can lead to a guest network
failure. (BZ#666800)

• Prior to this update, starting multiple para-virtualized guests in quick

succession could cause several instances of a hot plug script to compete for the
same lock file. Consequently, the connection may have timed out with the
following error message written to standard error:

Error: Device [id] (vbd) could not be connected. Hotplug scripts not working.

This update applies a patch that corrects the locking mechanism, so that such
timeouts no longer occur. (BZ#678282)

• Previously, creating a new domain caused a hot plug script to perform an

additional check of disk sharing capabilities. With a large number of virtual
block devices (VBDs), this operation could take a long time, and an attempt to
create a new domain could fail due to a timeout. Since a similar checking
mechanism is already implemented in the xend service, this update removes this
algorithm from the hot plug script, so that it no longer causes a domain
creation to fail. (BZ#680927)

Users of xen are advised to upgrade to these updated packages, which resolve
these issues. Note that after installation, the xend service must be restarted
for this update to take effect.

Solution

Before applying this update, make sure that all previously-released errata
relevant to your system have been applied.

This update is available via Red Hat Network. Details on how to use the Red
Hat Network to apply this update are available at
https://access.redhat.com/kb/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 ia64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 i386

Fixes

• BZ - 666800 - [5.4][Xen]When many guests are created by "xm create", the boot time increases quadratically with the number of total VBDs
• BZ - 678282 - Backport upstream fixes to vbd hotplug
• BZ - 680927 - Domain creation failed when previous domains have lots of vbds

CVEs

(none)

References

(none)