mmu_page_add_parent_pte(cache, sp, sptep);
- if (sp->unsync_children || sp->unsync)
+ /*
+ * The non-direct sub-pagetable must be updated before linking. For
+ * L1 sp, the pagetable is updated via kvm_sync_page() in
+ * kvm_mmu_find_shadow_page() without write-protecting the gfn,
+ * so sp->unsync can be true or false. For higher level non-direct
+ * sp, the pagetable is updated/synced via mmu_sync_children() in
+ * FNAME(fetch)(), so sp->unsync_children can only be false.
+ * WARN_ON_ONCE() if anything happens unexpectedly.
+ */
+ if (WARN_ON_ONCE(sp->unsync_children) || sp->unsync)
mark_unsync(sptep);
}