[PATCH mm-unstable v1 23/26] um/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

David Hildenbrand
2023-01-13T17:10:23Z

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by using bit 10, which is
yet unused for swap PTEs.

The pte_mkuptodate() is a bit weird in __pte_to_swp_entry() for a swap PTE
... but it only messes with bit 1 and 2 and there is a comment in
set_pte(), so leave these bits alone.

While at it, mask the type in __swp_entry().

Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/um/include/asm/pgtable.h | 37 +++++++++++++++++++++++++++++++++--
1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index 4e3052f2671a..cedc5fd451ce 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -21,6 +21,9 @@
#define _PAGE_PROTNONE 0x010 /* if the user mapped it with PROT_NONE;
pte_present gives true */

+/* We borrow bit 10 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE 0x400
+
#ifdef CONFIG_3_LEVEL_PGTABLES
#include <asm/pgtable-3level.h>
#else
@@ -288,16 +291,46 @@ extern pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr);

#define update_mmu_cache(vma,address,ptep) do {} while (0)

-/* Encode and de-code a swap entry */
+/*
+ * 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 1 0
+ *
+ * E is the exclusive marker that is not stored in swap entries.
+ * _PAGE_NEWPAGE (bit 1) is always set to 1 in set_pte().
+ */
#define __swp_type(x) (((x).val >> 5) & 0x1f)
#define __swp_offset(x) ((x).val >> 11)

#define __swp_entry(type, offset) \
- ((swp_entry_t) { ((type) << 5) | ((offset) << 11) })
+ ((swp_entry_t) { (((type) & 0x1f) << 5) | ((offset) << 11) })
#define __pte_to_swp_entry(pte) \
((swp_entry_t) { pte_val(pte_mkuptodate(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_get_bits(pte, _PAGE_SWP_EXCLUSIVE);
+}
+
+static inline pte_t pte_swp_mkexclusive(pte_t pte)
+{
+ pte_set_bits(pte, _PAGE_SWP_EXCLUSIVE);
+ return pte;
+}
+
+static inline pte_t pte_swp_clear_exclusive(pte_t pte)
+{
+ pte_clear_bits(pte, _PAGE_SWP_EXCLUSIVE);
+ return pte;
+}
+
/* Clear a kernel PTE and flush it from the TLB */
#define kpte_clear_flush(ptep, vaddr) \
do { \
--
2.39.0