Pull x86 fix from Peter Anvin:
"A single fix to not invoke the espfix code on Xen PV, as it turns out
to oops the guest when invoked after all. This patch leaves some
amount of dead code, in particular unnecessary initialization of the
espfix stacks when they won't be used, but in the interest of keeping
the patch minimal that cleanup can wait for the next cycle"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86_64/entry/xen: Do not invoke espfix64 on Xen