The MITRE CVE dictionary describes this issue as:
The create_pit_timer function in arch/x86/kvm/i8254.c in KVM 83, and possibly other versions, does not properly handle when Programmable Interval Timer (PIT) interrupt requests (IRQs) when a virtual interrupt controller (irqchip) is not available, which allows local users to cause a denial of service (NULL pointer dereference) by starting a timer.
Find out more about CVE-2011-4622 from the
MITRE CVE dictionary dictionary and
This issue did not affect the versions of Linux kernel as shipped with Red Hat Enterprise Linux 4 and Red Hat Enterprise MRG as they did not provide support for the KVM subsystem. It has been addressed in Red Hat Enterprise 5 and 6 via https://rhn.redhat.com/errata/RHSA-2012-0051.html and https://rhn.redhat.com/errata/RHSA-2012-0350.html.