From 93c0eac40d4e3ce4d5a3c6e0dc74eceaf8f63e0d Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 13 Jan 2023 18:10:24 +0100 Subject: [PATCH] x86/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE also on 32bit Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE just like we already do on x86-64. After deciphering the PTE layout it becomes clear that there are still unused bits for 2-level and 3-level page tables that we should be able to use. Reusing a bit avoids stealing one bit from the swap offset. While at it, mask the type in __swp_entry(); use some helper definitions to make the macros easier to grasp. Link: https://lkml.kernel.org/r/20230113171026.582290-25-david@redhat.com Signed-off-by: David Hildenbrand Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Signed-off-by: Andrew Morton --- arch/x86/include/asm/pgtable-2level.h | 26 +++++++++++++++++++++----- arch/x86/include/asm/pgtable-3level.h | 26 +++++++++++++++++++++++--- arch/x86/include/asm/pgtable.h | 2 -- 3 files changed, 44 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/pgtable-2level.h b/arch/x86/include/asm/pgtable-2level.h index 60d0f90..e9482a1 100644 --- a/arch/x86/include/asm/pgtable-2level.h +++ b/arch/x86/include/asm/pgtable-2level.h @@ -80,21 +80,37 @@ static inline unsigned long pte_bitop(unsigned long value, unsigned int rightshi return ((value >> rightshift) & mask) << leftshift; } -/* 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 ------------------> 0 E <- type --> 0 + * + * E is the exclusive marker that is not stored in swap entries. + */ #define SWP_TYPE_BITS 5 +#define _SWP_TYPE_MASK ((1U << SWP_TYPE_BITS) - 1) +#define _SWP_TYPE_SHIFT (_PAGE_BIT_PRESENT + 1) #define SWP_OFFSET_SHIFT (_PAGE_BIT_PROTNONE + 1) -#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(x) (((x).val >> (_PAGE_BIT_PRESENT + 1)) \ - & ((1U << SWP_TYPE_BITS) - 1)) +#define __swp_type(x) (((x).val >> _SWP_TYPE_SHIFT) \ + & _SWP_TYPE_MASK) #define __swp_offset(x) ((x).val >> SWP_OFFSET_SHIFT) #define __swp_entry(type, offset) ((swp_entry_t) { \ - ((type) << (_PAGE_BIT_PRESENT + 1)) \ + (((type) & _SWP_TYPE_MASK) << _SWP_TYPE_SHIFT) \ | ((offset) << SWP_OFFSET_SHIFT) }) #define __pte_to_swp_entry(pte) ((swp_entry_t) { (pte).pte_low }) #define __swp_entry_to_pte(x) ((pte_t) { .pte = (x).val }) +/* We borrow bit 7 to store the exclusive marker in swap PTEs. */ +#define _PAGE_SWP_EXCLUSIVE _PAGE_PSE + /* No inverted PFNs on 2 level page tables */ static inline u64 protnone_mask(u64 val) diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h index 967b135..9e7c0b7 100644 --- a/arch/x86/include/asm/pgtable-3level.h +++ b/arch/x86/include/asm/pgtable-3level.h @@ -145,8 +145,24 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, } #endif -/* 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: + * + * 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 + * < type -> <---------------------- offset ---------------------- + * + * 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 E 0 0 0 0 0 0 0 + * + * E is the exclusive marker that is not stored in swap entries. + */ #define SWP_TYPE_BITS 5 +#define _SWP_TYPE_MASK ((1U << SWP_TYPE_BITS) - 1) #define SWP_OFFSET_FIRST_BIT (_PAGE_BIT_PROTNONE + 1) @@ -154,9 +170,10 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, #define SWP_OFFSET_SHIFT (SWP_OFFSET_FIRST_BIT + SWP_TYPE_BITS) #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS) -#define __swp_type(x) (((x).val) & ((1UL << SWP_TYPE_BITS) - 1)) +#define __swp_type(x) (((x).val) & _SWP_TYPE_MASK) #define __swp_offset(x) ((x).val >> SWP_TYPE_BITS) -#define __swp_entry(type, offset) ((swp_entry_t){(type) | (offset) << SWP_TYPE_BITS}) +#define __swp_entry(type, offset) ((swp_entry_t){((type) & _SWP_TYPE_MASK) \ + | (offset) << SWP_TYPE_BITS}) /* * Normally, __swp_entry() converts from arch-independent swp_entry_t to @@ -184,6 +201,9 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, #define __pte_to_swp_entry(pte) (__swp_entry(__pteval_swp_type(pte), \ __pteval_swp_offset(pte))) +/* We borrow bit 7 to store the exclusive marker in swap PTEs. */ +#define _PAGE_SWP_EXCLUSIVE _PAGE_PSE + #include #endif /* _ASM_X86_PGTABLE_3LEVEL_H */ diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 1c84339..d251957 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1299,7 +1299,6 @@ static inline void update_mmu_cache_pud(struct vm_area_struct *vma, unsigned long addr, pud_t *pud) { } -#ifdef _PAGE_SWP_EXCLUSIVE #define __HAVE_ARCH_PTE_SWP_EXCLUSIVE static inline pte_t pte_swp_mkexclusive(pte_t pte) { @@ -1315,7 +1314,6 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) { return pte_clear_flags(pte, _PAGE_SWP_EXCLUSIVE); } -#endif /* _PAGE_SWP_EXCLUSIVE */ #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY static inline pte_t pte_swp_mksoft_dirty(pte_t pte) -- 2.7.4