1 /* mmu-context.c: MMU context allocation and management
2 *
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #include <linux/sched.h>
13 #include <linux/mm.h>
14 #include <asm/tlbflush.h>
15
16 #define NR_CXN 4096
17
18 static unsigned long cxn_bitmap[NR_CXN / (sizeof(unsigned long) * 8)];
19 static LIST_HEAD(cxn_owners_lru);
20 static DEFINE_SPINLOCK(cxn_owners_lock);
21
22 int __nongpreldata cxn_pinned = -1;
23
24
25 /*****************************************************************************/
26 /*
27 * initialise a new context
28 */
init_new_context(struct task_struct * tsk,struct mm_struct * mm)29 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
30 {
31 memset(&mm->context, 0, sizeof(mm->context));
32 INIT_LIST_HEAD(&mm->context.id_link);
33 mm->context.itlb_cached_pge = 0xffffffffUL;
34 mm->context.dtlb_cached_pge = 0xffffffffUL;
35
36 return 0;
37 } /* end init_new_context() */
38
39 /*****************************************************************************/
40 /*
41 * make sure a kernel MMU context has a CPU context number
42 * - call with cxn_owners_lock held
43 */
get_cxn(mm_context_t * ctx)44 static unsigned get_cxn(mm_context_t *ctx)
45 {
46 struct list_head *_p;
47 mm_context_t *p;
48 unsigned cxn;
49
50 if (!list_empty(&ctx->id_link)) {
51 list_move_tail(&ctx->id_link, &cxn_owners_lru);
52 }
53 else {
54 /* find the first unallocated context number
55 * - 0 is reserved for the kernel
56 */
57 cxn = find_next_zero_bit(cxn_bitmap, NR_CXN, 1);
58 if (cxn < NR_CXN) {
59 set_bit(cxn, cxn_bitmap);
60 }
61 else {
62 /* none remaining - need to steal someone else's cxn */
63 p = NULL;
64 list_for_each(_p, &cxn_owners_lru) {
65 p = list_entry(_p, mm_context_t, id_link);
66 if (!p->id_busy && p->id != cxn_pinned)
67 break;
68 }
69
70 BUG_ON(_p == &cxn_owners_lru);
71
72 cxn = p->id;
73 p->id = 0;
74 list_del_init(&p->id_link);
75 __flush_tlb_mm(cxn);
76 }
77
78 ctx->id = cxn;
79 list_add_tail(&ctx->id_link, &cxn_owners_lru);
80 }
81
82 return ctx->id;
83 } /* end get_cxn() */
84
85 /*****************************************************************************/
86 /*
87 * restore the current TLB miss handler mapped page tables into the MMU context and set up a
88 * mapping for the page directory
89 */
change_mm_context(mm_context_t * old,mm_context_t * ctx,pgd_t * pgd)90 void change_mm_context(mm_context_t *old, mm_context_t *ctx, pgd_t *pgd)
91 {
92 unsigned long _pgd;
93
94 _pgd = virt_to_phys(pgd);
95
96 /* save the state of the outgoing MMU context */
97 old->id_busy = 0;
98
99 asm volatile("movsg scr0,%0" : "=r"(old->itlb_cached_pge));
100 asm volatile("movsg dampr4,%0" : "=r"(old->itlb_ptd_mapping));
101 asm volatile("movsg scr1,%0" : "=r"(old->dtlb_cached_pge));
102 asm volatile("movsg dampr5,%0" : "=r"(old->dtlb_ptd_mapping));
103
104 /* select an MMU context number */
105 spin_lock(&cxn_owners_lock);
106 get_cxn(ctx);
107 ctx->id_busy = 1;
108 spin_unlock(&cxn_owners_lock);
109
110 asm volatile("movgs %0,cxnr" : : "r"(ctx->id));
111
112 /* restore the state of the incoming MMU context */
113 asm volatile("movgs %0,scr0" : : "r"(ctx->itlb_cached_pge));
114 asm volatile("movgs %0,dampr4" : : "r"(ctx->itlb_ptd_mapping));
115 asm volatile("movgs %0,scr1" : : "r"(ctx->dtlb_cached_pge));
116 asm volatile("movgs %0,dampr5" : : "r"(ctx->dtlb_ptd_mapping));
117
118 /* map the PGD into uncached virtual memory */
119 asm volatile("movgs %0,ttbr" : : "r"(_pgd));
120 asm volatile("movgs %0,dampr3"
121 :: "r"(_pgd | xAMPRx_L | xAMPRx_M | xAMPRx_SS_16Kb |
122 xAMPRx_S | xAMPRx_C | xAMPRx_V));
123
124 } /* end change_mm_context() */
125
126 /*****************************************************************************/
127 /*
128 * finished with an MMU context number
129 */
destroy_context(struct mm_struct * mm)130 void destroy_context(struct mm_struct *mm)
131 {
132 mm_context_t *ctx = &mm->context;
133
134 spin_lock(&cxn_owners_lock);
135
136 if (!list_empty(&ctx->id_link)) {
137 if (ctx->id == cxn_pinned)
138 cxn_pinned = -1;
139
140 list_del_init(&ctx->id_link);
141 clear_bit(ctx->id, cxn_bitmap);
142 __flush_tlb_mm(ctx->id);
143 ctx->id = 0;
144 }
145
146 spin_unlock(&cxn_owners_lock);
147 } /* end destroy_context() */
148
149 /*****************************************************************************/
150 /*
151 * display the MMU context currently a process is currently using
152 */
153 #ifdef CONFIG_PROC_FS
proc_pid_status_frv_cxnr(struct mm_struct * mm,char * buffer)154 char *proc_pid_status_frv_cxnr(struct mm_struct *mm, char *buffer)
155 {
156 spin_lock(&cxn_owners_lock);
157 buffer += sprintf(buffer, "CXNR: %u\n", mm->context.id);
158 spin_unlock(&cxn_owners_lock);
159
160 return buffer;
161 } /* end proc_pid_status_frv_cxnr() */
162 #endif
163
164 /*****************************************************************************/
165 /*
166 * (un)pin a process's mm_struct's MMU context ID
167 */
cxn_pin_by_pid(pid_t pid)168 int cxn_pin_by_pid(pid_t pid)
169 {
170 struct task_struct *tsk;
171 struct mm_struct *mm = NULL;
172 int ret;
173
174 /* unpin if pid is zero */
175 if (pid == 0) {
176 cxn_pinned = -1;
177 return 0;
178 }
179
180 ret = -ESRCH;
181
182 /* get a handle on the mm_struct */
183 read_lock(&tasklist_lock);
184 tsk = find_task_by_vpid(pid);
185 if (tsk) {
186 ret = -EINVAL;
187
188 task_lock(tsk);
189 if (tsk->mm) {
190 mm = tsk->mm;
191 atomic_inc(&mm->mm_users);
192 ret = 0;
193 }
194 task_unlock(tsk);
195 }
196 read_unlock(&tasklist_lock);
197
198 if (ret < 0)
199 return ret;
200
201 /* make sure it has a CXN and pin it */
202 spin_lock(&cxn_owners_lock);
203 cxn_pinned = get_cxn(&mm->context);
204 spin_unlock(&cxn_owners_lock);
205
206 mmput(mm);
207 return 0;
208 } /* end cxn_pin_by_pid() */
209