arm64: mte: Lock a page for MTE tag initialisation

[linux-2.6-microblaze.git] / arch / arm64 / include / asm / mte.h

diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index 3f8199b..20dd06d 100644 (file)
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -25,7 +25,7 @@ unsigned long mte_copy_tags_to_user(void __user *to, void *from,
                                    unsigned long n);
 int mte_save_tags(struct page *page);
 void mte_save_page_tags(const void *page_addr, void *tag_storage);
-bool mte_restore_tags(swp_entry_t entry, struct page *page);
+void mte_restore_tags(swp_entry_t entry, struct page *page);
 void mte_restore_page_tags(void *page_addr, const void *tag_storage);
 void mte_invalidate_tags(int type, pgoff_t offset);
 void mte_invalidate_tags_area(int type);
@@ -36,6 +36,8 @@ void mte_free_tag_storage(char *storage);
 
 /* track which pages have valid allocation tags */
 #define PG_mte_tagged  PG_arch_2
+/* simple lock to avoid multiple threads tagging the same page */
+#define PG_mte_lock    PG_arch_3
 
 static inline void set_page_mte_tagged(struct page *page)
 {
@@ -60,6 +62,33 @@ static inline bool page_mte_tagged(struct page *page)
        return ret;
 }
 
+/*
+ * Lock the page for tagging and return 'true' if the page can be tagged,
+ * 'false' if already tagged. PG_mte_tagged is never cleared and therefore the
+ * locking only happens once for page initialisation.
+ *
+ * The page MTE lock state:
+ *
+ *   Locked:   PG_mte_lock && !PG_mte_tagged
+ *   Unlocked: !PG_mte_lock || PG_mte_tagged
+ *
+ * Acquire semantics only if the page is tagged (returning 'false').
+ */
+static inline bool try_page_mte_tagging(struct page *page)
+{
+       if (!test_and_set_bit(PG_mte_lock, &page->flags))
+               return true;
+
+       /*
+        * The tags are either being initialised or may have been initialised
+        * already. Check if the PG_mte_tagged flag has been set or wait
+        * otherwise.
+        */
+       smp_cond_load_acquire(&page->flags, VAL & (1UL << PG_mte_tagged));
+
+       return false;
+}
+
 void mte_zero_clear_page_tags(void *addr);
 void mte_sync_tags(pte_t old_pte, pte_t pte);
 void mte_copy_page_tags(void *kto, const void *kfrom);
@@ -86,6 +115,10 @@ static inline bool page_mte_tagged(struct page *page)
 {
        return false;
 }
+static inline bool try_page_mte_tagging(struct page *page)
+{
+       return false;
+}
 static inline void mte_zero_clear_page_tags(void *addr)
 {
 }