[PATCH v2 4/6] s390/mm: Make PTC and UV call order consistent

[Alexander Gordeev]

In various code paths, page_table_check_pte_clear() is called
before converting a secure page, while in others it is called
after. Make this consistent and always perform the conversion
after the PTC hook has been called. Also make all conversion‑
eligibility condition checks look the same, and rework the one
in ptep_get_and_clear_full() slightly.

Acked-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
---
 arch/s390/include/asm/pgtable.h | 39 +++++++++++++++------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 42688ea4337f..010a33fec867 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -1219,10 +1219,10 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 	pte_t res;
 
 	res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
+	page_table_check_pte_clear(mm, addr, res);
 	/* At this point the reference through the mapping is still present */
 	if (mm_is_protected(mm) && pte_present(res))
 		WARN_ON_ONCE(uv_convert_from_secure_pte(res));
-	page_table_check_pte_clear(mm, addr, res);
 	return res;
 }
 
@@ -1238,10 +1238,10 @@ static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
 	pte_t res;
 
 	res = ptep_xchg_direct(vma->vm_mm, addr, ptep, __pte(_PAGE_INVALID));
+	page_table_check_pte_clear(vma->vm_mm, addr, res);
 	/* At this point the reference through the mapping is still present */
 	if (mm_is_protected(vma->vm_mm) && pte_present(res))
 		WARN_ON_ONCE(uv_convert_from_secure_pte(res));
-	page_table_check_pte_clear(vma->vm_mm, addr, res);
 	return res;
 }
 
@@ -1265,26 +1265,23 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 	} else {
 		res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
 	}
-
 	page_table_check_pte_clear(mm, addr, res);
-
-	/* Nothing to do */
-	if (!mm_is_protected(mm) || !pte_present(res))
-		return res;
-	/*
-	 * At this point the reference through the mapping is still present.
-	 * The notifier should have destroyed all protected vCPUs at this
-	 * point, so the destroy should be successful.
-	 */
-	if (full && !uv_destroy_pte(res))
-		return res;
-	/*
-	 * If something went wrong and the page could not be destroyed, or
-	 * if this is not a mm teardown, the slower export is used as
-	 * fallback instead. If even that fails, print a warning and leak
-	 * the page, to avoid crashing the whole system.
-	 */
-	WARN_ON_ONCE(uv_convert_from_secure_pte(res));
+	/* At this point the reference through the mapping is still present */
+	if (mm_is_protected(mm) && pte_present(res)) {
+		/*
+		 * The notifier should have destroyed all protected vCPUs at
+		 * this point, so the destroy should be successful.
+		 */
+		if (full && !uv_destroy_pte(res))
+			return res;
+		/*
+		 * If something went wrong and the page could not be destroyed,
+		 * or if this is not a mm teardown, the slower export is used
+		 * as fallback instead. If even that fails, print a warning and
+		 * leak the page, to avoid crashing the whole system.
+		 */
+		WARN_ON_ONCE(uv_convert_from_secure_pte(res));
+	}
 	return res;
 }
 
-- 
2.51.0