[PATCH v3 5/5] arm64: pgtable: Warn unexpected pmdp_test_and_clear_young()

[Yicong Yang]

From: Yicong Yang <yangyicong at hisilicon.com>

Young bit operation on PMD table entry is only supported if
FEAT_HAFT enabled system widely. Add a warning for notifying
the misbehaviour.

Signed-off-by: Yicong Yang <yangyicong at hisilicon.com>
---
 arch/arm64/include/asm/pgtable.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e4712b969aba..bb0600a24016 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1265,6 +1265,8 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
 					    pmd_t *pmdp)
 {
+	/* Operation applies to PMD table entry only if FEAT_HAFT is enabled */
+	VM_WARN_ON(pmd_table(READ_ONCE(*pmdp)) && !system_support_haft());
 	return __ptep_test_and_clear_young(vma, address, (pte_t *)pmdp);
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */
-- 
2.24.0