[PATCH mm-unstable RFC 02/26] alpha/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
From: David Hildenbrand <hidden>
Date: 2022-12-06 14:50:24
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:
alpha port, the rest · Maintainers:
Richard Henderson, Matt Turner, Magnus Lindholm, Linus Torvalds
Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the type. Generic MM currently only uses 5 bits for the type (MAX_SWAPFILES_SHIFT), so the stolen bit is effectively unused. While at it, mask the type in mk_swap_pte() as well. Note that 32bit alpha has 64bit PTEs but only 32bit swap entries. So the lower 32bit are zero in a swap PTE and we could have taken a bit in there as well. Cc: Richard Henderson <richard.henderson@linaro.org> Cc: Ivan Kokshaysky <redacted> Cc: Matt Turner <mattst88@gmail.com> Signed-off-by: David Hildenbrand <redacted> --- arch/alpha/include/asm/pgtable.h | 41 ++++++++++++++++++++++++++++---- 1 file changed, 37 insertions(+), 4 deletions(-)
diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h
index 9e45f6735d5d..970abf511b13 100644
--- a/arch/alpha/include/asm/pgtable.h
+++ b/arch/alpha/include/asm/pgtable.h@@ -74,6 +74,9 @@ struct vm_area_struct; #define _PAGE_DIRTY 0x20000 #define _PAGE_ACCESSED 0x40000 +/* We borrow bit 39 to store the exclusive marker in swap PTEs. */ +#define _PAGE_SWP_EXCLUSIVE 0x8000000000UL + /* * NOTE! The "accessed" bit isn't necessarily exact: it can be kept exactly * by software (use the KRE/URE/KWE/UWE bits appropriately), but I'll fake it.
@@ -301,18 +304,48 @@ extern inline void update_mmu_cache(struct vm_area_struct * vma, } /* - * Non-present pages: high 24 bits are offset, next 8 bits type, - * low 32 bits zero. + * Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that + * are !pte_none() && !pte_present(). + * + * Format of swap PTEs: + * + * 6 6 6 6 5 5 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 4 4 3 3 3 3 3 3 3 3 + * 3 2 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 + * <------------------- offset ------------------> E <--- type --> + * + * 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 + * <--------------------------- zeroes --------------------------> + * + * E is the exclusive marker that is not stored in swap entries. */ extern inline pte_t mk_swap_pte(unsigned long type, unsigned long offset) -{ pte_t pte; pte_val(pte) = (type << 32) | (offset << 40); return pte; } +{ pte_t pte; pte_val(pte) = ((type & 0x7f) << 32) | (offset << 40); return pte; } -#define __swp_type(x) (((x).val >> 32) & 0xff) +#define __swp_type(x) (((x).val >> 32) & 0x7f) #define __swp_offset(x) ((x).val >> 40) #define __swp_entry(type, off) ((swp_entry_t) { pte_val(mk_swap_pte((type), (off))) }) #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; +} + #define pte_ERROR(e) \ printk("%s:%d: bad pte %016lx.\n", __FILE__, __LINE__, pte_val(e)) #define pmd_ERROR(e) \
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2.38.1