Hi, Keir, I find that Win2k3 guest will sometimes write back data to Read-only registers, and it is caused by "bt" instruction. The attached tiny patch is to disable writeback for bt instruction. Signed-off-by: Xu Dongxiao <dongxiao.xu@intel.com> Best Regards, --Dongxiao _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel