From a9a934f278613885816aa9f177968c1dac557240 Mon Sep 17 00:00:00 2001 From: Haavard Skinnemoen Date: Mon, 14 Jan 2008 23:11:26 +0100 Subject: [PATCH] avr32: Cover the kernel page tables in the user PGDs Expand the per-process PGDs so that they cover the kernel virtual memory area as well. This simplifies the TLB miss handler fastpath since it doesn't have to check for kernel addresses anymore. If a TLB miss happens on a kernel address and a second-level page table can't be found, we check swapper_pg_dir and copy the PGD entry into the user PGD if it can be found there. Signed-off-by: Haavard Skinnemoen --- arch/avr32/kernel/entry-avr32b.S | 42 ++++++++++++++++++++++++-------- include/asm-avr32/pgalloc.h | 14 ++++++++--- 2 files changed, 42 insertions(+), 14 deletions(-) diff --git a/arch/avr32/kernel/entry-avr32b.S b/arch/avr32/kernel/entry-avr32b.S index 3cdd7071f3..2b398cae11 100644 --- a/arch/avr32/kernel/entry-avr32b.S +++ b/arch/avr32/kernel/entry-avr32b.S @@ -98,10 +98,6 @@ tlb_miss_common: mfsr r0, SYSREG_TLBEAR mfsr r1, SYSREG_PTBR - /* Is it the vmalloc space? */ - bld r0, 31 - brcs handle_vmalloc_miss - /* * First level lookup: The PGD contains virtual pointers to * the second-level page tables, but they may be NULL if not @@ -143,15 +139,13 @@ pgtbl_lookup: tlbmiss_restore rete -handle_vmalloc_miss: - /* Simply do the lookup in init's page table */ - mov r1, lo(swapper_pg_dir) - orh r1, hi(swapper_pg_dir) - rjmp pgtbl_lookup - /* The slow path of the TLB miss handler */ .align 2 page_table_not_present: + /* Do we need to synchronize with swapper_pg_dir? */ + bld r0, 31 + brcs sync_with_swapper_pg_dir + page_not_present: tlbmiss_restore sub sp, 4 @@ -162,6 +156,34 @@ page_not_present: rcall do_page_fault rjmp ret_from_exception + .align 2 +sync_with_swapper_pg_dir: + /* + * If swapper_pg_dir contains a non-NULL second-level page + * table pointer, copy it into the current PGD. If not, we + * must handle it as a full-blown page fault. + * + * Jumping back to pgtbl_lookup causes an unnecessary lookup, + * but it is guaranteed to be a cache hit, it won't happen + * very often, and we absolutely do not want to sacrifice any + * performance in the fast path in order to improve this. + */ + mov r1, lo(swapper_pg_dir) + orh r1, hi(swapper_pg_dir) + ld.w r3, r1[r2 << 2] + cp.w r3, 0 + breq page_not_present + mfsr r1, SYSREG_PTBR + st.w r1[r2 << 2], r3 + rjmp pgtbl_lookup + + /* + * We currently have two bytes left at this point until we + * crash into the system call handler... + * + * Don't worry, the assembler will let us know. + */ + /* --- System Call --- */ diff --git a/include/asm-avr32/pgalloc.h b/include/asm-avr32/pgalloc.h index 5b768fc238..e9636d1f38 100644 --- a/include/asm-avr32/pgalloc.h +++ b/include/asm-avr32/pgalloc.h @@ -9,8 +9,6 @@ #define __ASM_AVR32_PGALLOC_H #include -#include -#include static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, pte_t *pte) @@ -30,12 +28,20 @@ static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd, */ static inline pgd_t *pgd_alloc(struct mm_struct *mm) { - return kcalloc(USER_PTRS_PER_PGD, sizeof(pgd_t), GFP_KERNEL); + pgd_t *pgd; + + pgd = (pgd_t *)get_zeroed_page(GFP_KERNEL | __GFP_REPEAT); + if (likely(pgd)) + memcpy(pgd + USER_PTRS_PER_PGD, + swapper_pg_dir + USER_PTRS_PER_PGD, + (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t)); + + return pgd; } static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd) { - kfree(pgd); + free_page((unsigned long)pgd); } static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm, -- 2.39.5