Comment 7 for bug 1157757

Some information that I got while discussion this upstream: This is a problem with Xen. In fact the same flags get used when doing a bare metal boot. The explanation for the different behaviour is that Xen does use paging even in non-paging mode of the guest (just a identity mapped table). SMEP would be ignored in real non-paging mode but in the Xen case it is used but the pages are not set up correctly.

Right now this can be worked-around by using "smep=0" as a hypervisor boot argument, or "nosmep" on the grub command line of the guest.

There was already a change that fixes a similar issue but in my testing it seems not to be in effect for this problem.