[PATCH mm-unstable RFC 10/26] m68k/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

From: David Hildenbrand
Date: Tue Dec 06 2022 - 09:53:14 EST

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit
from the type. Generic MM currently only uses 5 bits for the type
(MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused.

While at it, make sure for sun3 that the valid bit never gets set by
properly masking it off and mask the type in __swp_entry().

Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Greg Ungerer <gerg@xxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
arch/m68k/include/asm/mcf_pgtable.h | 36 ++++++++++++++++++++--
arch/m68k/include/asm/motorola_pgtable.h | 38 +++++++++++++++++++++--
arch/m68k/include/asm/sun3_pgtable.h | 39 ++++++++++++++++++++++--
3 files changed, 104 insertions(+), 9 deletions(-)

diff --git a/arch/m68k/include/asm/mcf_pgtable.h b/arch/m68k/include/asm/mcf_pgtable.h
index b619b22823f8..3f8f4d0e66dd 100644
--- a/arch/m68k/include/asm/mcf_pgtable.h
+++ b/arch/m68k/include/asm/mcf_pgtable.h
@@ -46,6 +46,9 @@
#define _CACHEMASK040 (~0x060)
#define _PAGE_GLOBAL040 0x400 /* 68040 global bit, used for kva descs */

+/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE 0x080
+
/*
* Externally used page protection values.
*/
@@ -254,15 +257,42 @@ static inline pte_t pte_mkcache(pte_t pte)
extern pgd_t kernel_pg_dir[PTRS_PER_PGD];

/*
- * Encode and de-code a swap entry (must be !pte_none(e) && !pte_present(e))
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ * Format of swap PTEs:
+ *
+ * 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
+ * 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+ * <------------------ offset -------------> 0 0 0 E <-- type --->
+ *
+ * E is the exclusive marker that is not stored in swap entries.
*/
-#define __swp_type(x) ((x).val & 0xFF)
+#define __swp_type(x) ((x).val & 0x7f)
#define __swp_offset(x) ((x).val >> 11)
-#define __swp_entry(typ, off) ((swp_entry_t) { (typ) | \
+#define __swp_entry(typ, off) ((swp_entry_t) { ((typ) & 0x7f) | \
(off << 11) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) (__pte((x).val))

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
#define pmd_pfn(pmd) (pmd_val(pmd) >> PAGE_SHIFT)
#define pmd_page(pmd) (pfn_to_page(pmd_val(pmd) >> PAGE_SHIFT))

diff --git a/arch/m68k/include/asm/motorola_pgtable.h b/arch/m68k/include/asm/motorola_pgtable.h
index 7ac3d64c6b33..02896027c781 100644
--- a/arch/m68k/include/asm/motorola_pgtable.h
+++ b/arch/m68k/include/asm/motorola_pgtable.h
@@ -41,6 +41,9 @@

#define _PAGE_PROTNONE 0x004

+/* We borrow bit 11 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE 0x800
+
#ifndef __ASSEMBLY__

/* This is the cache mode to be used for pages containing page descriptors for
@@ -169,12 +172,41 @@ static inline pte_t pte_mkcache(pte_t pte)
#define swapper_pg_dir kernel_pg_dir
extern pgd_t kernel_pg_dir[128];

-/* Encode and de-code a swap entry (must be !pte_none(e) && !pte_present(e)) */
-#define __swp_type(x) (((x).val >> 4) & 0xff)
+/*
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ * Format of swap PTEs:
+ *
+ * 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
+ * 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+ * <----------------- offset ------------> E <-- type ---> 0 0 0 0
+ *
+ * E is the exclusive marker that is not stored in swap entries.
+ */
+#define __swp_type(x) (((x).val >> 4) & 0x7f)
#define __swp_offset(x) ((x).val >> 12)
-#define __swp_entry(type, offset) ((swp_entry_t) { ((type) << 4) | ((offset) << 12) })
+#define __swp_entry(type, offset) ((swp_entry_t) { (((type) & 0x7f) << 4) | ((offset) << 12) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
#endif /* !__ASSEMBLY__ */
#endif /* _MOTOROLA_PGTABLE_H */
diff --git a/arch/m68k/include/asm/sun3_pgtable.h b/arch/m68k/include/asm/sun3_pgtable.h
index 90d57e537eb1..5e03ce4fd8d5 100644
--- a/arch/m68k/include/asm/sun3_pgtable.h
+++ b/arch/m68k/include/asm/sun3_pgtable.h
@@ -71,6 +71,9 @@
#define SUN3_PMD_MASK (0x0000003F)
#define SUN3_PMD_MAGIC (0x0000002B)

+/* We borrow bit 6 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE 0x040
+
#ifndef __ASSEMBLY__

/*
@@ -152,12 +155,42 @@ static inline pte_t pte_mkcache(pte_t pte) { return pte; }
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
extern pgd_t kernel_pg_dir[PTRS_PER_PGD];

-/* Macros to (de)construct the fake PTEs representing swap pages. */
-#define __swp_type(x) ((x).val & 0x7F)
+/*
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
+ * Format of swap PTEs:
+ *
+ * 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
+ * 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+ * 0 <--------------------- offset ----------------> E <- type -->
+ *
+ * E is the exclusive marker that is not stored in swap entries.
+ */
+#define __swp_type(x) ((x).val & 0x3f)
#define __swp_offset(x) (((x).val) >> 7)
-#define __swp_entry(type,offset) ((swp_entry_t) { ((type) | ((offset) << 7)) })
+#define __swp_entry(type,offset) ((swp_entry_t) { (((type) & 0x3f) | \
+ (((offset) << 7) & ~SUN3_PAGE_VALID)) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
+ return pte;
+}
+
#endif /* !__ASSEMBLY__ */
#endif /* !_SUN3_PGTABLE_H */
--
2.38.1