1 files changed, 10 insertions, 1 deletions

diff --git a/arch/x86/include/asm/pgtable-invert.h b/arch/x86/include/asm/pgtable-invert.h
index 44b1203ece12..a0c1525f1b6f 100644
--- a/arch/x86/include/asm/pgtable-invert.h
+++ b/arch/x86/include/asm/pgtable-invert.h
@@ -4,9 +4,18 @@
 
 #ifndef __ASSEMBLY__
 
+/*
+ * A clear pte value is special, and doesn't get inverted.
+ *
+ * Note that even users that only pass a pgprot_t (rather
+ * than a full pte) won't trigger the special zero case,
+ * because even PAGE_NONE has _PAGE_PROTNONE | _PAGE_ACCESSED
+ * set. So the all zero case really is limited to just the
+ * cleared page table entry case.
+ */
 static inline bool __pte_needs_invert(u64 val)
 {
-        return !(val & _PAGE_PRESENT);
+        return val && !(val & _PAGE_PRESENT);
 }
 
 /* Get a mask to xor with the page table entry to get the correct pfn. */