xen: disable interrupts before saving in percpu
xen: disable interrupts before saving in percpu

Impact: Fix race condition

xen_mc_batch has a small preempt race where it takes the address of a
percpu variable immediately before disabling interrupts, thereby
leaving a small window in which we may migrate to another cpu and save
the flags in the wrong percpu variable.  Disable interrupts before
saving the old flags in a percpu.

Signed-off-by: Jeremy Fitzhardinge <35cfe9f678a9e9bbdcf2f6e68cd105ce06d149b1@citrix.com>
Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas