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Diffstat (limited to 'arch/tile/include/asm/mmu_context.h')
| -rw-r--r-- | arch/tile/include/asm/mmu_context.h | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/arch/tile/include/asm/mmu_context.h b/arch/tile/include/asm/mmu_context.h new file mode 100644 index 00000000000..9bc0d0725c2 --- /dev/null +++ b/arch/tile/include/asm/mmu_context.h @@ -0,0 +1,131 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + */ + +#ifndef _ASM_TILE_MMU_CONTEXT_H +#define _ASM_TILE_MMU_CONTEXT_H + +#include <linux/smp.h> +#include <asm/setup.h> +#include <asm/page.h> +#include <asm/pgalloc.h> +#include <asm/pgtable.h> +#include <asm/tlbflush.h> +#include <asm/homecache.h> +#include <asm-generic/mm_hooks.h> + +static inline int +init_new_context(struct task_struct *tsk, struct mm_struct *mm) +{ + return 0; +} + +/* Note that arch/tile/kernel/head.S also calls hv_install_context() */ +static inline void __install_page_table(pgd_t *pgdir, int asid, pgprot_t prot) +{ + /* FIXME: DIRECTIO should not always be set. FIXME. */ + int rc = hv_install_context(__pa(pgdir), prot, asid, HV_CTX_DIRECTIO); + if (rc < 0) + panic("hv_install_context failed: %d", rc); +} + +static inline void install_page_table(pgd_t *pgdir, int asid) +{ + pte_t *ptep = virt_to_pte(NULL, (unsigned long)pgdir); + __install_page_table(pgdir, asid, *ptep); +} + +/* + * "Lazy" TLB mode is entered when we are switching to a kernel task, + * which borrows the mm of the previous task. The goal of this + * optimization is to avoid having to install a new page table. On + * early x86 machines (where the concept originated) you couldn't do + * anything short of a full page table install for invalidation, so + * handling a remote TLB invalidate required doing a page table + * re-install. Someone clearly decided that it was silly to keep + * doing this while in "lazy" TLB mode, so the optimization involves + * installing the swapper page table instead the first time one + * occurs, and clearing the cpu out of cpu_vm_mask, so the cpu running + * the kernel task doesn't need to take any more interrupts. At that + * point it's then necessary to explicitly reinstall it when context + * switching back to the original mm. + * + * On Tile, we have to do a page-table install whenever DMA is enabled, + * so in that case lazy mode doesn't help anyway. And more generally, + * we have efficient per-page TLB shootdown, and don't expect to spend + * that much time in kernel tasks in general, so just leaving the + * kernel task borrowing the old page table, but handling TLB + * shootdowns, is a reasonable thing to do. And importantly, this + * lets us use the hypervisor's internal APIs for TLB shootdown, which + * means we don't have to worry about having TLB shootdowns blocked + * when Linux is disabling interrupts; see the page migration code for + * an example of where it's important for TLB shootdowns to complete + * even when interrupts are disabled at the Linux level. + */ +static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *t) +{ +#if CHIP_HAS_TILE_DMA() + /* + * We have to do an "identity" page table switch in order to + * clear any pending DMA interrupts. + */ + if (current->thread.tile_dma_state.enabled) + install_page_table(mm->pgd, __get_cpu_var(current_asid)); +#endif +} + +static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, + struct task_struct *tsk) +{ + if (likely(prev != next)) { + + int cpu = smp_processor_id(); + + /* Pick new ASID. */ + int asid = __get_cpu_var(current_asid) + 1; + if (asid > max_asid) { + asid = min_asid; + local_flush_tlb(); + } + __get_cpu_var(current_asid) = asid; + + /* Clear cpu from the old mm, and set it in the new one. */ + cpumask_clear_cpu(cpu, &prev->cpu_vm_mask); + cpumask_set_cpu(cpu, &next->cpu_vm_mask); + + /* Re-load page tables */ + install_page_table(next->pgd, asid); + + /* See how we should set the red/black cache info */ + check_mm_caching(prev, next); + + /* + * Since we're changing to a new mm, we have to flush + * the icache in case some physical page now being mapped + * has subsequently been repurposed and has new code. + */ + __flush_icache(); + + } +} + +static inline void activate_mm(struct mm_struct *prev_mm, + struct mm_struct *next_mm) +{ + switch_mm(prev_mm, next_mm, NULL); +} + +#define destroy_context(mm) do { } while (0) +#define deactivate_mm(tsk, mm) do { } while (0) + +#endif /* _ASM_TILE_MMU_CONTEXT_H */ |