x86 PV guest INVLPG-like flushes may leave stale TLB entries

ISSUE DESCRIPTION x86 PV guest kernels may use hypercalls with INVLPG-like behavior to invalidate TLB entries even after changes to non-leaf page tables. Such changes to non-leaf page tables will, however, also render stale possible TLB entries created by Xen's internal use of linear page tables ...