linux-kernel - [PATCH mm-unstable RFC 14/26] nios2/mm: support __HAVE_ARCH_PTE_SWP

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Date:   Tue,  6 Dec 2022 15:47:18 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Nadav Amit <namit@...are.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>, linux-mm@...ck.org,
        x86@...nel.org, linux-alpha@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org,
        linux-mips@...r.kernel.org, openrisc@...ts.librecores.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org,
        David Hildenbrand <david@...hat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Subject: [PATCH mm-unstable RFC 14/26] nios2/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by using the yet-unused bit
31.

Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 arch/nios2/include/asm/pgtable-bits.h |  3 +++
 arch/nios2/include/asm/pgtable.h      | 22 +++++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/nios2/include/asm/pgtable-bits.h b/arch/nios2/include/asm/pgtable-bits.h
index bfddff383e89..724f9b08b1d1 100644
--- a/arch/nios2/include/asm/pgtable-bits.h
+++ b/arch/nios2/include/asm/pgtable-bits.h
@@ -31,4 +31,7 @@
 #define _PAGE_ACCESSED	(1<<26)	/* page referenced */
 #define _PAGE_DIRTY	(1<<27)	/* dirty page */
 
+/* We borrow bit 31 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE	(1<<31)
+
 #endif /* _ASM_NIOS2_PGTABLE_BITS_H */
diff --git a/arch/nios2/include/asm/pgtable.h b/arch/nios2/include/asm/pgtable.h
index d1e5c9eb4643..05999da01731 100644
--- a/arch/nios2/include/asm/pgtable.h
+++ b/arch/nios2/include/asm/pgtable.h
@@ -239,7 +239,9 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
  *
  *   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 < type -> 0 0 0 0 0 0 <-------------- offset --------------->
+ *   E < type -> 0 0 0 0 0 0 <-------------- offset --------------->
+ *
+ *   E is the exclusive marker that is not stored in swap entries.
  *
  * Note that the offset field is always non-zero if the swap type is 0, thus
  * !pte_none() is always true.
@@ -251,6 +253,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
 #define __swp_entry_to_pte(swp)	((pte_t) { (swp).val })
 #define __pte_to_swp_entry(pte)	((swp_entry_t) { pte_val(pte) })
 
+#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;
+}
+
 extern void __init paging_init(void);
 extern void __init mmu_init(void);
 
-- 
2.38.1