[PATCH v2 4/8] arm64/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

David Hildenbrand
2022-03-29T16:48:12Z

Let's use one of the type bits: core-mm only supports 5, so there is no
need to consume 6.

Note that we might be able to reuse bit 1, but reusing bit 1 turned out
problematic in the past for PROT_NONE handling; so let's play safe and
use another bit.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/arm64/include/asm/pgtable-prot.h | 1 +
arch/arm64/include/asm/pgtable.h | 23 ++++++++++++++++++++---
2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index b1e1b74d993c..62e0ebeed720 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -14,6 +14,7 @@
* Software defined PTE bits definition.
*/
#define PTE_WRITE (PTE_DBM) /* same as DBM (51) */
+#define PTE_SWP_EXCLUSIVE (_AT(pteval_t, 1) << 2) /* only for swp ptes */
#define PTE_DIRTY (_AT(pteval_t, 1) << 55)
#define PTE_SPECIAL (_AT(pteval_t, 1) << 56)
#define PTE_DEVMAP (_AT(pteval_t, 1) << 57)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 94e147e5456c..ad9b221963d4 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -402,6 +402,22 @@ static inline pgprot_t mk_pmd_sect_prot(pgprot_t prot)
return __pgprot((pgprot_val(prot) & ~PMD_TABLE_BIT) | PMD_TYPE_SECT);
}

+#define __HAVE_ARCH_PTE_SWP_EXCLUSIVE
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ return set_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
+}
+
+static inline int pte_swp_exclusive(pte_t pte)
+{
+ return pte_val(pte) & PTE_SWP_EXCLUSIVE;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ return clear_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
+}
+
#ifdef CONFIG_NUMA_BALANCING
/*
* See the comment in include/linux/pgtable.h
@@ -909,12 +925,13 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
/*
* Encode and decode a swap entry:
* bits 0-1: present (must be zero)
- * bits 2-7: swap type
+ * bits 2: remember PG_anon_exclusive
+ * bits 3-7: swap type
* bits 8-57: swap offset
* bit 58: PTE_PROT_NONE (must be zero)
*/
-#define __SWP_TYPE_SHIFT 2
-#define __SWP_TYPE_BITS 6
+#define __SWP_TYPE_SHIFT 3
+#define __SWP_TYPE_BITS 5
#define __SWP_OFFSET_BITS 50
#define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1)
#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT)
--
2.35.1