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From:   David Hildenbrand <david@redhat.com>
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        David Hildenbrand <david@redhat.com>
Subject: [PATCH v1 5/7] s390/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date:   Tue, 15 Mar 2022 15:18:35 +0100
Message-Id: <20220315141837.137118-6-david@redhat.com>
In-Reply-To: <20220315141837.137118-1-david@redhat.com>
References: <20220315141837.137118-1-david@redhat.com>
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Let's steal one bit from the offset. While at it, document the meaning
of bit 62 for swap ptes.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/s390/include/asm/pgtable.h | 37 ++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 008a6c856fa4..c182212a2b44 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -181,6 +181,8 @@ static inline int is_module_addr(void *addr)
 #define _PAGE_SOFT_DIRTY 0x000
 #endif
 
+#define _PAGE_SWP_EXCLUSIVE _PAGE_LARGE	/* SW pte exclusive swap bit */
+
 /* Set of bits not changed in pte_modify */
 #define _PAGE_CHG_MASK		(PAGE_MASK | _PAGE_SPECIAL | _PAGE_DIRTY | \
 				 _PAGE_YOUNG | _PAGE_SOFT_DIRTY)
@@ -796,6 +798,24 @@ static inline int pmd_protnone(pmd_t pmd)
 }
 #endif
 
+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+	pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+	return pte;
+}
+
+static inline int pte_swp_exclusive(pte_t pte)
+{
+	return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+	pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+	return pte;
+}
+
 static inline int pte_soft_dirty(pte_t pte)
 {
 	return pte_val(pte) & _PAGE_SOFT_DIRTY;
@@ -1675,16 +1695,19 @@ static inline int has_transparent_hugepage(void)
  * information in the lowcore.
  * Bits 54 and 63 are used to indicate the page type.
  * A swap pte is indicated by bit pattern (pte & 0x201) == 0x200
- * This leaves the bits 0-51 and bits 56-62 to store type and offset.
- * We use the 5 bits from 57-61 for the type and the 52 bits from 0-51
+ * This leaves the bits 0-50 and bits 56-61 to store type and offset.
+ * We use the 5 bits from 57-61 for the type and the 51 bits from 0-50
  * for the offset.
- * |			  offset			|01100|type |00|
- * |0000000000111111111122222222223333333333444444444455|55555|55566|66|
- * |0123456789012345678901234567890123456789012345678901|23456|78901|23|
+ * |			  offset		       |E|01100|type |S0|
+ * |000000000011111111112222222222333333333344444444445|5|55555|55566|66|
+ * |012345678901234567890123456789012345678901234567890|1|23456|78901|23|
+ *
+ * S (bit 62) is used for softdirty tracking.
+ * E (bit 51) is used to remember PG_anon_exclusive.
  */
 
-#define __SWP_OFFSET_MASK	((1UL << 52) - 1)
-#define __SWP_OFFSET_SHIFT	12
+#define __SWP_OFFSET_MASK	((1UL << 51) - 1)
+#define __SWP_OFFSET_SHIFT	13
 #define __SWP_TYPE_MASK		((1UL << 5) - 1)
 #define __SWP_TYPE_SHIFT	2
 
-- 
2.35.1