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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