[PATCH mm-unstable v1 06/26] hexagon/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

David Hildenbrand
2023-01-13T17:10:06Z

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the
offset. This reduces the maximum swap space per file to 16 GiB (was 32
GiB).

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

Cc: Brian Cain <bcain@quicinc.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/hexagon/include/asm/pgtable.h | 37 +++++++++++++++++++++++++-----
1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/arch/hexagon/include/asm/pgtable.h b/arch/hexagon/include/asm/pgtable.h
index f7048c18b6f9..7eb008e477c8 100644
--- a/arch/hexagon/include/asm/pgtable.h
+++ b/arch/hexagon/include/asm/pgtable.h
@@ -61,6 +61,9 @@ extern unsigned long empty_zero_page;
* So we'll put up with a bit of inefficiency for now...
*/

+/* We borrow bit 6 to store the exclusive marker in swap PTEs. */
+#define _PAGE_SWP_EXCLUSIVE (1<<6)
+
/*
* Top "FOURTH" level (pgd), which for the Hexagon VM is really
* only the second from the bottom, pgd and pud both being collapsed.
@@ -359,9 +362,12 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
#define ZERO_PAGE(vaddr) (virt_to_page(&empty_zero_page))

/*
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
+ *
* Swap/file PTE definitions. If _PAGE_PRESENT is zero, the rest of the PTE is
* interpreted as swap information. The remaining free bits are interpreted as
- * swap type/offset tuple. Rather than have the TLB fill handler test
+ * listed below. Rather than have the TLB fill handler test
* _PAGE_PRESENT, we're going to reserve the permissions bits and set them to
* all zeros for swap entries, which speeds up the miss handler at the cost of
* 3 bits of offset. That trade-off can be revisited if necessary, but Hexagon
@@ -371,9 +377,10 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
* Format of swap PTE:
* bit 0: Present (zero)
* bits 1-5: swap type (arch independent layer uses 5 bits max)
- * bits 6-9: bits 3:0 of offset
+ * bit 6: exclusive marker
+ * bits 7-9: bits 2:0 of offset
* bits 10-12: effectively _PAGE_PROTNONE (all zero)
- * bits 13-31: bits 22:4 of swap offset
+ * bits 13-31: bits 21:3 of swap offset
*
* The split offset makes some of the following macros a little gnarly,
* but there's plenty of precedent for this sort of thing.
@@ -383,11 +390,29 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
#define __swp_type(swp_pte) (((swp_pte).val >> 1) & 0x1f)

#define __swp_offset(swp_pte) \
- ((((swp_pte).val >> 6) & 0xf) | (((swp_pte).val >> 9) & 0x7ffff0))
+ ((((swp_pte).val >> 7) & 0x7) | (((swp_pte).val >> 10) & 0x3ffff8))

#define __swp_entry(type, offset) \
((swp_entry_t) { \
- ((type << 1) | \
- ((offset & 0x7ffff0) << 9) | ((offset & 0xf) << 6)) })
+ (((type & 0x1f) << 1) | \
+ ((offset & 0x3ffff8) << 10) | ((offset & 0x7) << 7)) })
+
+#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
--
2.39.0