summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorDavid Hildenbrand <david@redhat.com>2023-01-13 18:10:13 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-02-02 22:33:08 -0800
commit0a9ad8273ff4643dd50ff6b3ec991ab270e87a89 (patch)
treee9beec3b782f365ca7063c6a772fe3adfa7e3bb5
parent83d3b2b46ea3f8fa542fb7528b3bca6f476d0fab (diff)
nios2/mm: refactor swap PTE layout
nios2 disables swap for a good reason: it doesn't even provide sufficient type bits as required by core MM. However, swap entries are nowadays also used for other purposes (migration entries, PTE markers, HWPoison, ...), and accidential use could be problematic. Let's properly use 5 bits for the swap type and document the layout. Bits 26--31 should get ignored by hardware completely, so they can be used. Link: https://lkml.kernel.org/r/20230113171026.582290-14-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Dinh Nguyen <dinguyen@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--arch/nios2/include/asm/pgtable.h18
1 files changed, 10 insertions, 8 deletions
diff --git a/arch/nios2/include/asm/pgtable.h b/arch/nios2/include/asm/pgtable.h
index ab793bc517f5..d1e5c9eb4643 100644
--- a/arch/nios2/include/asm/pgtable.h
+++ b/arch/nios2/include/asm/pgtable.h
@@ -232,19 +232,21 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
__FILE__, __LINE__, pgd_val(e))
/*
- * Encode and decode a swap entry (must be !pte_none(pte) && !pte_present(pte):
+ * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
+ * are !pte_none() && !pte_present().
*
- * 31 30 29 28 27 26 25 24 23 22 21 20 19 18 ... 1 0
- * 0 0 0 0 type. 0 0 0 0 0 0 offset.........
+ * Format of swap PTEs:
*
- * This gives us up to 2**2 = 4 swap files and 2**20 * 4K = 4G per swap file.
+ * 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 --------------->
*
- * Note that the offset field is always non-zero, thus !pte_none(pte) is always
- * true.
+ * Note that the offset field is always non-zero if the swap type is 0, thus
+ * !pte_none() is always true.
*/
-#define __swp_type(swp) (((swp).val >> 26) & 0x3)
+#define __swp_type(swp) (((swp).val >> 26) & 0x1f)
#define __swp_offset(swp) ((swp).val & 0xfffff)
-#define __swp_entry(type, off) ((swp_entry_t) { (((type) & 0x3) << 26) \
+#define __swp_entry(type, off) ((swp_entry_t) { (((type) & 0x1f) << 26) \
| ((off) & 0xfffff) })
#define __swp_entry_to_pte(swp) ((pte_t) { (swp).val })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })