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/sched/mm.h>
14 #include <linux/sched/task.h>
15 #include <linux/mm.h>
16 #include <asm/tlbflush.h>
17
18 #define NR_CXN 4096
19
20 static unsigned long cxn_bitmap[NR_CXN / (sizeof(unsigned long) * 8)];
21 static LIST_HEAD(cxn_owners_lru);
22 static DEFINE_SPINLOCK(cxn_owners_lock);
23
24 int __nongpreldata cxn_pinned = -1;
25
26
27 /*****************************************************************************/
28 /*
29 * initialise a new context
30 */
init_new_context(struct task_struct * tsk,struct mm_struct * mm)31 int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
32 {
33 memset(&mm->context, 0, sizeof(mm->context));
34 INIT_LIST_HEAD(&mm->context.id_link);
35 mm->context.itlb_cached_pge = 0xffffffffUL;
36 mm->context.dtlb_cached_pge = 0xffffffffUL;
37
38 return 0;
39 } /* end init_new_context() */
40
41 /*****************************************************************************/
42 /*
43 * make sure a kernel MMU context has a CPU context number
44 * - call with cxn_owners_lock held
45 */
get_cxn(mm_context_t * ctx)46 static unsigned get_cxn(mm_context_t *ctx)
47 {
48 struct list_head *_p;
49 mm_context_t *p;
50 unsigned cxn;
51
52 if (!list_empty(&ctx->id_link)) {
53 list_move_tail(&ctx->id_link, &cxn_owners_lru);
54 }
55 else {
56 /* find the first unallocated context number
57 * - 0 is reserved for the kernel
58 */
59 cxn = find_next_zero_bit(cxn_bitmap, NR_CXN, 1);
60 if (cxn < NR_CXN) {
61 set_bit(cxn, cxn_bitmap);
62 }
63 else {
64 /* none remaining - need to steal someone else's cxn */
65 p = NULL;
66 list_for_each(_p, &cxn_owners_lru) {
67 p = list_entry(_p, mm_context_t, id_link);
68 if (!p->id_busy && p->id != cxn_pinned)
69 break;
70 }
71
72 BUG_ON(_p == &cxn_owners_lru);
73
74 cxn = p->id;
75 p->id = 0;
76 list_del_init(&p->id_link);
77 __flush_tlb_mm(cxn);
78 }
79
80 ctx->id = cxn;
81 list_add_tail(&ctx->id_link, &cxn_owners_lru);
82 }
83
84 return ctx->id;
85 } /* end get_cxn() */
86
87 /*****************************************************************************/
88 /*
89 * restore the current TLB miss handler mapped page tables into the MMU context and set up a
90 * mapping for the page directory
91 */
change_mm_context(mm_context_t * old,mm_context_t * ctx,pgd_t * pgd)92 void change_mm_context(mm_context_t *old, mm_context_t *ctx, pgd_t *pgd)
93 {
94 unsigned long _pgd;
95
96 _pgd = virt_to_phys(pgd);
97
98 /* save the state of the outgoing MMU context */
99 old->id_busy = 0;
100
101 asm volatile("movsg scr0,%0" : "=r"(old->itlb_cached_pge));
102 asm volatile("movsg dampr4,%0" : "=r"(old->itlb_ptd_mapping));
103 asm volatile("movsg scr1,%0" : "=r"(old->dtlb_cached_pge));
104 asm volatile("movsg dampr5,%0" : "=r"(old->dtlb_ptd_mapping));
105
106 /* select an MMU context number */
107 spin_lock(&cxn_owners_lock);
108 get_cxn(ctx);
109 ctx->id_busy = 1;
110 spin_unlock(&cxn_owners_lock);
111
112 asm volatile("movgs %0,cxnr" : : "r"(ctx->id));
113
114 /* restore the state of the incoming MMU context */
115 asm volatile("movgs %0,scr0" : : "r"(ctx->itlb_cached_pge));
116 asm volatile("movgs %0,dampr4" : : "r"(ctx->itlb_ptd_mapping));
117 asm volatile("movgs %0,scr1" : : "r"(ctx->dtlb_cached_pge));
118 asm volatile("movgs %0,dampr5" : : "r"(ctx->dtlb_ptd_mapping));
119
120 /* map the PGD into uncached virtual memory */
121 asm volatile("movgs %0,ttbr" : : "r"(_pgd));
122 asm volatile("movgs %0,dampr3"
123 :: "r"(_pgd | xAMPRx_L | xAMPRx_M | xAMPRx_SS_16Kb |
124 xAMPRx_S | xAMPRx_C | xAMPRx_V));
125
126 } /* end change_mm_context() */
127
128 /*****************************************************************************/
129 /*
130 * finished with an MMU context number
131 */
destroy_context(struct mm_struct * mm)132 void destroy_context(struct mm_struct *mm)
133 {
134 mm_context_t *ctx = &mm->context;
135
136 spin_lock(&cxn_owners_lock);
137
138 if (!list_empty(&ctx->id_link)) {
139 if (ctx->id == cxn_pinned)
140 cxn_pinned = -1;
141
142 list_del_init(&ctx->id_link);
143 clear_bit(ctx->id, cxn_bitmap);
144 __flush_tlb_mm(ctx->id);
145 ctx->id = 0;
146 }
147
148 spin_unlock(&cxn_owners_lock);
149 } /* end destroy_context() */
150
151 /*****************************************************************************/
152 /*
153 * display the MMU context currently a process is currently using
154 */
155 #ifdef CONFIG_PROC_FS
proc_pid_status_frv_cxnr(struct mm_struct * mm,char * buffer)156 char *proc_pid_status_frv_cxnr(struct mm_struct *mm, char *buffer)
157 {
158 spin_lock(&cxn_owners_lock);
159 buffer += sprintf(buffer, "CXNR: %u\n", mm->context.id);
160 spin_unlock(&cxn_owners_lock);
161
162 return buffer;
163 } /* end proc_pid_status_frv_cxnr() */
164 #endif
165
166 /*****************************************************************************/
167 /*
168 * (un)pin a process's mm_struct's MMU context ID
169 */
cxn_pin_by_pid(pid_t pid)170 int cxn_pin_by_pid(pid_t pid)
171 {
172 struct task_struct *tsk;
173 struct mm_struct *mm = NULL;
174 int ret;
175
176 /* unpin if pid is zero */
177 if (pid == 0) {
178 cxn_pinned = -1;
179 return 0;
180 }
181
182 ret = -ESRCH;
183
184 /* get a handle on the mm_struct */
185 read_lock(&tasklist_lock);
186 tsk = find_task_by_vpid(pid);
187 if (tsk) {
188 ret = -EINVAL;
189
190 task_lock(tsk);
191 if (tsk->mm) {
192 mm = tsk->mm;
193 mmget(mm);
194 ret = 0;
195 }
196 task_unlock(tsk);
197 }
198 read_unlock(&tasklist_lock);
199
200 if (ret < 0)
201 return ret;
202
203 /* make sure it has a CXN and pin it */
204 spin_lock(&cxn_owners_lock);
205 cxn_pinned = get_cxn(&mm->context);
206 spin_unlock(&cxn_owners_lock);
207
208 mmput(mm);
209 return 0;
210 } /* end cxn_pin_by_pid() */
211