[PATCH mm-unstable RFC 25/26] xtensa/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
From: David Hildenbrand <hidden>
Date: 2022-12-06 14:59:00
Also in:
linux-alpha, linux-arm-kernel, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, loongarch, sparclinux
Subsystem:
tensilica xtensa port (xtensa), the rest · Maintainers:
Chris Zankel, Max Filippov, Linus Torvalds
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by using bit 1. This bit should be safe to use for our usecase. Most importantly, we can still distinguish swap PTEs from PAGE_NONE PTEs (see pte_present()) and don't use one of the two reserved attribute masks (1101 and 1111). Attribute mask 1100 and 1110 now identify swap PTEs. While at it, remove SWP_TYPE_BITS (not really helpful as it's not used in the actual swap macros) and mask the type in __swp_entry(). Cc: Chris Zankel <chris@zankel.net> Cc: Max Filippov <jcmvbkbc@gmail.com> Signed-off-by: David Hildenbrand <redacted> --- arch/xtensa/include/asm/pgtable.h | 32 ++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-)
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index 5b5484d707b2..1025e2dc292b 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h@@ -96,7 +96,7 @@ * +- - - - - - - - - - - - - - - - - - - - -+ * (PAGE_NONE)| PPN | 0 | 00 | ADW | 01 | 11 | 11 | * +-----------------------------------------+ - * swap | index | type | 01 | 11 | 00 | + * swap | index | type | 01 | 11 | e0 | * +-----------------------------------------+ * * For T1050 hardware and earlier the layout differs for present and (PAGE_NONE)
@@ -112,6 +112,7 @@ * RI ring (0=privileged, 1=user, 2 and 3 are unused) * CA cache attribute: 00 bypass, 01 writeback, 10 writethrough * (11 is invalid and used to mark pages that are not present) + * e exclusive marker in swap PTEs * w page is writable (hw) * x page is executable (hw) * index swap offset / PAGE_SIZE (bit 11-31: 21 bits -> 8 GB)
@@ -158,6 +159,9 @@ #define _PAGE_DIRTY (1<<7) /* software: page dirty */ #define _PAGE_ACCESSED (1<<8) /* software: page accessed (read) */ +/* We borrow bit 1 to store the exclusive marker in swap PTEs. */ +#define _PAGE_SWP_EXCLUSIVE (1<<1) + #ifdef CONFIG_MMU #define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
@@ -343,19 +347,37 @@ ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr, pte_t *ptep) } /* - * Encode and decode a swap and file entry. + * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that + * are !pte_none() && !pte_present(). */ -#define SWP_TYPE_BITS 5 -#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS) +#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5) #define __swp_type(entry) (((entry).val >> 6) & 0x1f) #define __swp_offset(entry) ((entry).val >> 11) #define __swp_entry(type,offs) \ - ((swp_entry_t){((type) << 6) | ((offs) << 11) | \ + ((swp_entry_t){(((type) & 0x1f) << 6) | ((offs) << 11) | \ _PAGE_CA_INVALID | _PAGE_USER}) #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(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_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 /* !defined (__ASSEMBLY__) */
--
2.38.1