Tweaked the patch to prevent IOMMU_WAIT_OP panicking on the kexec path. 
Unfortunately, this has to rely on the kexecing variable.

As with the other hacks in this patch, I cant see a better way of
solving the problem.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com