1/* 2 * Copyright 2010 Tilera Corporation. All Rights Reserved. 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation, version 2. 7 * 8 * This program is distributed in the hope that it will be useful, but 9 * WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or 11 * NON INFRINGEMENT. See the GNU General Public License for 12 * more details. 13 */ 14 15#ifndef _ASM_TILE_MMU_CONTEXT_H 16#define _ASM_TILE_MMU_CONTEXT_H 17 18#include <linux/smp.h> 19#include <linux/mm_types.h> 20 21#include <asm/setup.h> 22#include <asm/page.h> 23#include <asm/pgalloc.h> 24#include <asm/pgtable.h> 25#include <asm/tlbflush.h> 26#include <asm/homecache.h> 27#include <asm-generic/mm_hooks.h> 28 29static inline int 30init_new_context(struct task_struct *tsk, struct mm_struct *mm) 31{ 32 return 0; 33} 34 35/* 36 * Note that arch/tile/kernel/head_NN.S and arch/tile/mm/migrate_NN.S 37 * also call hv_install_context(). 38 */ 39static inline void __install_page_table(pgd_t *pgdir, int asid, pgprot_t prot) 40{ 41 /* FIXME: DIRECTIO should not always be set. FIXME. */ 42 int rc = hv_install_context(__pa(pgdir), prot, asid, 43 HV_CTX_DIRECTIO | CTX_PAGE_FLAG); 44 if (rc < 0) 45 panic("hv_install_context failed: %d", rc); 46} 47 48static inline void install_page_table(pgd_t *pgdir, int asid) 49{ 50 pte_t *ptep = virt_to_kpte((unsigned long)pgdir); 51 __install_page_table(pgdir, asid, *ptep); 52} 53 54/* 55 * "Lazy" TLB mode is entered when we are switching to a kernel task, 56 * which borrows the mm of the previous task. The goal of this 57 * optimization is to avoid having to install a new page table. On 58 * early x86 machines (where the concept originated) you couldn't do 59 * anything short of a full page table install for invalidation, so 60 * handling a remote TLB invalidate required doing a page table 61 * re-install. Someone clearly decided that it was silly to keep 62 * doing this while in "lazy" TLB mode, so the optimization involves 63 * installing the swapper page table instead the first time one 64 * occurs, and clearing the cpu out of cpu_vm_mask, so the cpu running 65 * the kernel task doesn't need to take any more interrupts. At that 66 * point it's then necessary to explicitly reinstall it when context 67 * switching back to the original mm. 68 * 69 * On Tile, we have to do a page-table install whenever DMA is enabled, 70 * so in that case lazy mode doesn't help anyway. And more generally, 71 * we have efficient per-page TLB shootdown, and don't expect to spend 72 * that much time in kernel tasks in general, so just leaving the 73 * kernel task borrowing the old page table, but handling TLB 74 * shootdowns, is a reasonable thing to do. And importantly, this 75 * lets us use the hypervisor's internal APIs for TLB shootdown, which 76 * means we don't have to worry about having TLB shootdowns blocked 77 * when Linux is disabling interrupts; see the page migration code for 78 * an example of where it's important for TLB shootdowns to complete 79 * even when interrupts are disabled at the Linux level. 80 */ 81static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *t) 82{ 83#if CHIP_HAS_TILE_DMA() 84 /* 85 * We have to do an "identity" page table switch in order to 86 * clear any pending DMA interrupts. 87 */ 88 if (current->thread.tile_dma_state.enabled) 89 install_page_table(mm->pgd, __this_cpu_read(current_asid)); 90#endif 91} 92 93static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, 94 struct task_struct *tsk) 95{ 96 if (likely(prev != next)) { 97 98 int cpu = smp_processor_id(); 99 100 /* Pick new ASID. */ 101 int asid = __this_cpu_read(current_asid) + 1; 102 if (asid > max_asid) { 103 asid = min_asid; 104 local_flush_tlb(); 105 } 106 __this_cpu_write(current_asid, asid); 107 108 /* Clear cpu from the old mm, and set it in the new one. */ 109 cpumask_clear_cpu(cpu, mm_cpumask(prev)); 110 cpumask_set_cpu(cpu, mm_cpumask(next)); 111 112 /* Re-load page tables */ 113 install_page_table(next->pgd, asid); 114 115 /* See how we should set the red/black cache info */ 116 check_mm_caching(prev, next); 117 118 /* 119 * Since we're changing to a new mm, we have to flush 120 * the icache in case some physical page now being mapped 121 * has subsequently been repurposed and has new code. 122 */ 123 __flush_icache(); 124 125 } 126} 127 128static inline void activate_mm(struct mm_struct *prev_mm, 129 struct mm_struct *next_mm) 130{ 131 switch_mm(prev_mm, next_mm, NULL); 132} 133 134#define destroy_context(mm) do { } while (0) 135#define deactivate_mm(tsk, mm) do { } while (0) 136 137#endif /* _ASM_TILE_MMU_CONTEXT_H */ 138