Intel Desktop and Intel Mobile Boards with BIOS firmware DQ35JO, DQ35MP, DP35DP, DG33FB, DG33BU, DG33TL, MGM965TW, D945GCPE, and DX38BT allows local administrators with ring 0 privileges to gain additional privileges and modify code that is running in System Management Mode, or access hypervisory memory as demonstrated at Black Hat 2008 by accessing certain remapping registers in Xen 3.3.
https://exchange.xforce.ibmcloud.com/vulnerabilities/44676
http://www.securityfocus.com/bid/30823
http://theinvisiblethings.blogspot.com/2008/08/intel-patches-q35-bug.html
http://theinvisiblethings.blogspot.com/2008/08/attacking-xen-domu-vs-dom0.html
http://security-center.intel.com/advisory.aspx?intelid=INTEL-SA-00017&languageid=en-fr