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Diffstat (limited to 'arch/powerpc/include/asm/book3s/64/pgtable.h')
-rw-r--r--arch/powerpc/include/asm/book3s/64/pgtable.h30
1 files changed, 30 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 7dede2e34b70..ccf00a8b98c6 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -876,6 +876,23 @@ static inline int pmd_present(pmd_t pmd)
return false;
}
+static inline int pmd_is_serializing(pmd_t pmd)
+{
+ /*
+ * If the pmd is undergoing a split, the _PAGE_PRESENT bit is clear
+ * and _PAGE_INVALID is set (see pmd_present, pmdp_invalidate).
+ *
+ * This condition may also occur when flushing a pmd while flushing
+ * it (see ptep_modify_prot_start), so callers must ensure this
+ * case is fine as well.
+ */
+ if ((pmd_raw(pmd) & cpu_to_be64(_PAGE_PRESENT | _PAGE_INVALID)) ==
+ cpu_to_be64(_PAGE_INVALID))
+ return true;
+
+ return false;
+}
+
static inline int pmd_bad(pmd_t pmd)
{
if (radix_enabled())
@@ -1092,6 +1109,19 @@ static inline int pmd_protnone(pmd_t pmd)
#define pmd_access_permitted pmd_access_permitted
static inline bool pmd_access_permitted(pmd_t pmd, bool write)
{
+ /*
+ * pmdp_invalidate sets this combination (which is not caught by
+ * !pte_present() check in pte_access_permitted), to prevent
+ * lock-free lookups, as part of the serialize_against_pte_lookup()
+ * synchronisation.
+ *
+ * This also catches the case where the PTE's hardware PRESENT bit is
+ * cleared while TLB is flushed, which is suboptimal but should not
+ * be frequent.
+ */
+ if (pmd_is_serializing(pmd))
+ return false;
+
return pte_access_permitted(pmd_pte(pmd), write);
}