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 <asm/setup.h>
20 #include <asm/page.h>
21 #include <asm/pgalloc.h>
22 #include <asm/pgtable.h>
23 #include <asm/tlbflush.h>
24 #include <asm/homecache.h>
25 #include <asm-generic/mm_hooks.h>
26
27 static inline int
init_new_context(struct task_struct * tsk,struct mm_struct * mm)28 init_new_context(struct task_struct *tsk, struct mm_struct *mm)
29 {
30 return 0;
31 }
32
33 /*
34 * Note that arch/tile/kernel/head_NN.S and arch/tile/mm/migrate_NN.S
35 * also call hv_install_context().
36 */
__install_page_table(pgd_t * pgdir,int asid,pgprot_t prot)37 static inline void __install_page_table(pgd_t *pgdir, int asid, pgprot_t prot)
38 {
39 /* FIXME: DIRECTIO should not always be set. FIXME. */
40 int rc = hv_install_context(__pa(pgdir), prot, asid,
41 HV_CTX_DIRECTIO | CTX_PAGE_FLAG);
42 if (rc < 0)
43 panic("hv_install_context failed: %d", rc);
44 }
45
install_page_table(pgd_t * pgdir,int asid)46 static inline void install_page_table(pgd_t *pgdir, int asid)
47 {
48 pte_t *ptep = virt_to_kpte((unsigned long)pgdir);
49 __install_page_table(pgdir, asid, *ptep);
50 }
51
52 /*
53 * "Lazy" TLB mode is entered when we are switching to a kernel task,
54 * which borrows the mm of the previous task. The goal of this
55 * optimization is to avoid having to install a new page table. On
56 * early x86 machines (where the concept originated) you couldn't do
57 * anything short of a full page table install for invalidation, so
58 * handling a remote TLB invalidate required doing a page table
59 * re-install. Someone clearly decided that it was silly to keep
60 * doing this while in "lazy" TLB mode, so the optimization involves
61 * installing the swapper page table instead the first time one
62 * occurs, and clearing the cpu out of cpu_vm_mask, so the cpu running
63 * the kernel task doesn't need to take any more interrupts. At that
64 * point it's then necessary to explicitly reinstall it when context
65 * switching back to the original mm.
66 *
67 * On Tile, we have to do a page-table install whenever DMA is enabled,
68 * so in that case lazy mode doesn't help anyway. And more generally,
69 * we have efficient per-page TLB shootdown, and don't expect to spend
70 * that much time in kernel tasks in general, so just leaving the
71 * kernel task borrowing the old page table, but handling TLB
72 * shootdowns, is a reasonable thing to do. And importantly, this
73 * lets us use the hypervisor's internal APIs for TLB shootdown, which
74 * means we don't have to worry about having TLB shootdowns blocked
75 * when Linux is disabling interrupts; see the page migration code for
76 * an example of where it's important for TLB shootdowns to complete
77 * even when interrupts are disabled at the Linux level.
78 */
enter_lazy_tlb(struct mm_struct * mm,struct task_struct * t)79 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *t)
80 {
81 #if CHIP_HAS_TILE_DMA()
82 /*
83 * We have to do an "identity" page table switch in order to
84 * clear any pending DMA interrupts.
85 */
86 if (current->thread.tile_dma_state.enabled)
87 install_page_table(mm->pgd, __this_cpu_read(current_asid));
88 #endif
89 }
90
switch_mm(struct mm_struct * prev,struct mm_struct * next,struct task_struct * tsk)91 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
92 struct task_struct *tsk)
93 {
94 if (likely(prev != next)) {
95
96 int cpu = smp_processor_id();
97
98 /* Pick new ASID. */
99 int asid = __this_cpu_read(current_asid) + 1;
100 if (asid > max_asid) {
101 asid = min_asid;
102 local_flush_tlb();
103 }
104 __this_cpu_write(current_asid, asid);
105
106 /* Clear cpu from the old mm, and set it in the new one. */
107 cpumask_clear_cpu(cpu, mm_cpumask(prev));
108 cpumask_set_cpu(cpu, mm_cpumask(next));
109
110 /* Re-load page tables */
111 install_page_table(next->pgd, asid);
112
113 /* See how we should set the red/black cache info */
114 check_mm_caching(prev, next);
115
116 /*
117 * Since we're changing to a new mm, we have to flush
118 * the icache in case some physical page now being mapped
119 * has subsequently been repurposed and has new code.
120 */
121 __flush_icache();
122
123 }
124 }
125
activate_mm(struct mm_struct * prev_mm,struct mm_struct * next_mm)126 static inline void activate_mm(struct mm_struct *prev_mm,
127 struct mm_struct *next_mm)
128 {
129 switch_mm(prev_mm, next_mm, NULL);
130 }
131
132 #define destroy_context(mm) do { } while (0)
133 #define deactivate_mm(tsk, mm) do { } while (0)
134
135 #endif /* _ASM_TILE_MMU_CONTEXT_H */
136