This bit will be used by idle page tracking code to correctly identify if a page that was swapped out was idle before it got swapped out. Without this PTE bit, we lose information about if a page is idle or not since the page frame gets unmapped.
In this patch we reuse PTE_DEVMAP bit since idle page tracking only works on user pages in the LRU. Device pages should not consitute those so it should be unused and safe to use. Cc: Robin Murphy <[email protected]> Signed-off-by: Joel Fernandes (Google) <[email protected]> --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/pgtable-prot.h | 1 + arch/arm64/include/asm/pgtable.h | 15 +++++++++++++++ 3 files changed, 17 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3adcec05b1f6..9d1412c693d7 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -128,6 +128,7 @@ config ARM64 select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_PREL32_RELOCATIONS + select HAVE_ARCH_PTE_SWP_PGIDLE select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_STACKLEAK select HAVE_ARCH_THREAD_STRUCT_WHITELIST diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index 92d2e9f28f28..917b15c5d63a 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -18,6 +18,7 @@ #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) #define PTE_DEVMAP (_AT(pteval_t, 1) << 57) #define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */ +#define PTE_SWP_PGIDLE PTE_DEVMAP /* for idle page tracking during swapout */ #ifndef __ASSEMBLY__ diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 3f5461f7b560..558f5ebd81ba 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -212,6 +212,21 @@ static inline pte_t pte_mkdevmap(pte_t pte) return set_pte_bit(pte, __pgprot(PTE_DEVMAP)); } +static inline int pte_swp_page_idle(pte_t pte) +{ + return 0; +} + +static inline pte_t pte_swp_mkpage_idle(pte_t pte) +{ + return set_pte_bit(pte, __pgprot(PTE_SWP_PGIDLE)); +} + +static inline pte_t pte_swp_clear_page_idle(pte_t pte) +{ + return clear_pte_bit(pte, __pgprot(PTE_SWP_PGIDLE)); +} + static inline void set_pte(pte_t *ptep, pte_t pte) { WRITE_ONCE(*ptep, pte); -- 2.22.0.770.g0f2c4a37fd-goog
