The vmx_set_msr function in arch/x86/kvm/vmx.c in the VMX implementation in the KVM subsystem in the Linux kernel before 2.6.29.1 on the i386 platform allows guest OS users to cause a denial of service (OOPS) by setting the EFER_LME (aka "Long mode enable") bit in the Extended Feature Enable Register (EFER) model-specific register, which is specific to the x86_64 platform.
https://www.redhat.com/archives/fedora-package-announce/2009-May/msg01126.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/49594
https://bugzilla.redhat.com/show_bug.cgi?id=502109
http://www.ubuntu.com/usn/usn-793-1
http://www.securityfocus.com/bid/34331
http://www.securityfocus.com/archive/1/503610/100/0/threaded
http://www.globalsecuritymag.com/Vigil-nce-Linux-kernel-denial-of%2C20090402%2C8311
http://www.debian.org/security/2009/dsa-1800
http://www.debian.org/security/2009/dsa-1787
http://vigilance.fr/vulnerability/Linux-kernel-denial-of-service-via-EFER-8585
http://secunia.com/advisories/35656
http://secunia.com/advisories/35394
http://secunia.com/advisories/35387
http://secunia.com/advisories/35226
http://secunia.com/advisories/35121
http://secunia.com/advisories/35120
http://secunia.com/advisories/34981
http://secunia.com/advisories/34478
http://patchwork.kernel.org/patch/15549/
http://openwall.com/lists/oss-security/2009/04/01/3
http://lists.opensuse.org/opensuse-security-announce/2009-06/msg00002.html
http://lists.opensuse.org/opensuse-security-announce/2009-06/msg00001.html