summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/mm/mmu_context_hash64.c
blob: 3bafc3deca6d66478161cca9db8bc2fb9107173a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
/*
 *  MMU context allocation for 64-bit kernels.
 *
 *  Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/slab.h>

#include <asm/mmu_context.h>

#ifdef CONFIG_PPC_ICSWX
/*
 * The processor and its L2 cache cause the icswx instruction to
 * generate a COP_REQ transaction on PowerBus. The transaction has
 * no address, and the processor does not perform an MMU access
 * to authenticate the transaction. The command portion of the
 * PowerBus COP_REQ transaction includes the LPAR_ID (LPID) and
 * the coprocessor Process ID (PID), which the coprocessor compares
 * to the authorized LPID and PID held in the coprocessor, to determine
 * if the process is authorized to generate the transaction.
 * The data of the COP_REQ transaction is 128-byte or less and is
 * placed in cacheable memory on a 128-byte cache line boundary.
 *
 * The task to use a coprocessor should use use_cop() to allocate
 * a coprocessor PID before executing icswx instruction. use_cop()
 * also enables the coprocessor context switching. Drop_cop() is
 * used to free the coprocessor PID.
 *
 * Example:
 * Host Fabric Interface (HFI) is a PowerPC network coprocessor.
 * Each HFI have multiple windows. Each HFI window serves as a
 * network device sending to and receiving from HFI network.
 * HFI immediate send function uses icswx instruction. The immediate
 * send function allows small (single cache-line) packets be sent
 * without using the regular HFI send FIFO and doorbell, which are
 * much slower than immediate send.
 *
 * For each task intending to use HFI immediate send, the HFI driver
 * calls use_cop() to obtain a coprocessor PID for the task.
 * The HFI driver then allocate a free HFI window and save the
 * coprocessor PID to the HFI window to allow the task to use the
 * HFI window.
 *
 * The HFI driver repeatedly creates immediate send packets and
 * issues icswx instruction to send data through the HFI window.
 * The HFI compares the coprocessor PID in the CPU PID register
 * to the PID held in the HFI window to determine if the transaction
 * is allowed.
 *
 * When the task to release the HFI window, the HFI driver calls
 * drop_cop() to release the coprocessor PID.
 */

#define COP_PID_NONE 0
#define COP_PID_MIN (COP_PID_NONE + 1)
#define COP_PID_MAX (0xFFFF)

static DEFINE_SPINLOCK(mmu_context_acop_lock);
static DEFINE_IDA(cop_ida);

void switch_cop(struct mm_struct *next)
{
	mtspr(SPRN_PID, next->context.cop_pid);
	mtspr(SPRN_ACOP, next->context.acop);
}

static int new_cop_pid(struct ida *ida, int min_id, int max_id,
		       spinlock_t *lock)
{
	int index;
	int err;

again:
	if (!ida_pre_get(ida, GFP_KERNEL))
		return -ENOMEM;

	spin_lock(lock);
	err = ida_get_new_above(ida, min_id, &index);
	spin_unlock(lock);

	if (err == -EAGAIN)
		goto again;
	else if (err)
		return err;

	if (index > max_id) {
		spin_lock(lock);
		ida_remove(ida, index);
		spin_unlock(lock);
		return -ENOMEM;
	}

	return index;
}

static void sync_cop(void *arg)
{
	struct mm_struct *mm = arg;

	if (mm == current->active_mm)
		switch_cop(current->active_mm);
}

/**
 * Start using a coprocessor.
 * @acop: mask of coprocessor to be used.
 * @mm: The mm the coprocessor to associate with. Most likely current mm.
 *
 * Return a positive PID if successful. Negative errno otherwise.
 * The returned PID will be fed to the coprocessor to determine if an
 * icswx transaction is authenticated.
 */
int use_cop(unsigned long acop, struct mm_struct *mm)
{
	int ret;

	if (!cpu_has_feature(CPU_FTR_ICSWX))
		return -ENODEV;

	if (!mm || !acop)
		return -EINVAL;

	/* We need to make sure mm_users doesn't change */
	down_read(&mm->mmap_sem);
	spin_lock(mm->context.cop_lockp);

	if (mm->context.cop_pid == COP_PID_NONE) {
		ret = new_cop_pid(&cop_ida, COP_PID_MIN, COP_PID_MAX,
				  &mmu_context_acop_lock);
		if (ret < 0)
			goto out;

		mm->context.cop_pid = ret;
	}
	mm->context.acop |= acop;

	sync_cop(mm);

	/*
	 * If this is a threaded process then there might be other threads
	 * running. We need to send an IPI to force them to pick up any
	 * change in PID and ACOP.
	 */
	if (atomic_read(&mm->mm_users) > 1)
		smp_call_function(sync_cop, mm, 1);

	ret = mm->context.cop_pid;

out:
	spin_unlock(mm->context.cop_lockp);
	up_read(&mm->mmap_sem);

	return ret;
}
EXPORT_SYMBOL_GPL(use_cop);

/**
 * Stop using a coprocessor.
 * @acop: mask of coprocessor to be stopped.
 * @mm: The mm the coprocessor associated with.
 */
void drop_cop(unsigned long acop, struct mm_struct *mm)
{
	int free_pid = COP_PID_NONE;

	if (!cpu_has_feature(CPU_FTR_ICSWX))
		return;

	if (WARN_ON_ONCE(!mm))
		return;

	/* We need to make sure mm_users doesn't change */
	down_read(&mm->mmap_sem);
	spin_lock(mm->context.cop_lockp);

	mm->context.acop &= ~acop;

	if ((!mm->context.acop) && (mm->context.cop_pid != COP_PID_NONE)) {
		free_pid = mm->context.cop_pid;
		mm->context.cop_pid = COP_PID_NONE;
	}

	sync_cop(mm);

	/*
	 * If this is a threaded process then there might be other threads
	 * running. We need to send an IPI to force them to pick up any
	 * change in PID and ACOP.
	 */
	if (atomic_read(&mm->mm_users) > 1)
		smp_call_function(sync_cop, mm, 1);

	if (free_pid != COP_PID_NONE) {
		spin_lock(&mmu_context_acop_lock);
		ida_remove(&cop_ida, free_pid);
		spin_unlock(&mmu_context_acop_lock);
	}

	spin_unlock(mm->context.cop_lockp);
	up_read(&mm->mmap_sem);
}
EXPORT_SYMBOL_GPL(drop_cop);

#endif /* CONFIG_PPC_ICSWX */

static DEFINE_SPINLOCK(mmu_context_lock);
static DEFINE_IDA(mmu_context_ida);

/*
 * The proto-VSID space has 2^35 - 1 segments available for user mappings.
 * Each segment contains 2^28 bytes.  Each context maps 2^44 bytes,
 * so we can support 2^19-1 contexts (19 == 35 + 28 - 44).
 */
#define MAX_CONTEXT	((1UL << 19) - 1)

int __init_new_context(void)
{
	int index;
	int err;

again:
	if (!ida_pre_get(&mmu_context_ida, GFP_KERNEL))
		return -ENOMEM;

	spin_lock(&mmu_context_lock);
	err = ida_get_new_above(&mmu_context_ida, 1, &index);
	spin_unlock(&mmu_context_lock);

	if (err == -EAGAIN)
		goto again;
	else if (err)
		return err;

	if (index > MAX_CONTEXT) {
		spin_lock(&mmu_context_lock);
		ida_remove(&mmu_context_ida, index);
		spin_unlock(&mmu_context_lock);
		return -ENOMEM;
	}

	return index;
}
EXPORT_SYMBOL_GPL(__init_new_context);

int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
	int index;

	index = __init_new_context();
	if (index < 0)
		return index;

	/* The old code would re-promote on fork, we don't do that
	 * when using slices as it could cause problem promoting slices
	 * that have been forced down to 4K
	 */
	if (slice_mm_new_context(mm))
		slice_set_user_psize(mm, mmu_virtual_psize);
	subpage_prot_init_new_context(mm);
	mm->context.id = index;
#ifdef CONFIG_PPC_ICSWX
	mm->context.cop_lockp = kmalloc(sizeof(spinlock_t), GFP_KERNEL);
	if (!mm->context.cop_lockp) {
		__destroy_context(index);
		subpage_prot_free(mm);
		mm->context.id = MMU_NO_CONTEXT;
		return -ENOMEM;
	}
	spin_lock_init(mm->context.cop_lockp);
#endif /* CONFIG_PPC_ICSWX */

	return 0;
}

void __destroy_context(int context_id)
{
	spin_lock(&mmu_context_lock);
	ida_remove(&mmu_context_ida, context_id);
	spin_unlock(&mmu_context_lock);
}
EXPORT_SYMBOL_GPL(__destroy_context);

void destroy_context(struct mm_struct *mm)
{
#ifdef CONFIG_PPC_ICSWX
	drop_cop(mm->context.acop, mm);
	kfree(mm->context.cop_lockp);
	mm->context.cop_lockp = NULL;
#endif /* CONFIG_PPC_ICSWX */
	__destroy_context(mm->context.id);
	subpage_prot_free(mm);
	mm->context.id = MMU_NO_CONTEXT;
}
OpenPOWER on IntegriCloud