aboutsummaryrefslogtreecommitdiffstats
path: root/arch/powerpc/mm/icswx.c
blob: 915412e4d5ba58d3b898afe502d89273b6945aad (plain) (blame)
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
/*
 *  ICSWX and ACOP Management
 *
 *  Copyright (C) 2011 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/types.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#include "icswx.h"

/*
 * 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 in size and is placed in cacheable
 * memory on a 128-byte cache line boundary.
 *
 * The task to use a coprocessor should use use_cop() to mark the use
 * of the Coprocessor Type (CT) and context switching. On a server
 * class processor, the PID register is used only for coprocessor
 * management + * and so a coprocessor PID is allocated before
 * executing icswx + * instruction. 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.
 */

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

/**
 * 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;

	/* The page_table_lock ensures mm_users won't change under us */
	spin_lock(&mm->page_table_lock);
	spin_lock(mm->context.cop_lockp);

	ret = get_cop_pid(mm);
	if (ret < 0)
		goto out;

	/* update acop */
	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);

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

	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;

	if (!cpu_has_feature(CPU_FTR_ICSWX))
		return;

	if (WARN_ON_ONCE(!mm))
		return;

	/* The page_table_lock ensures mm_users won't change under us */
	spin_lock(&mm->page_table_lock);
	spin_lock(mm->context.cop_lockp);

	mm->context.acop &= ~acop;

	free_pid = disable_cop_pid(mm);
	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)
		free_cop_pid(free_pid);

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

static int acop_use_cop(int ct)
{
	/* There is no alternate policy, yet */
	return -1;
}

/*
 * Get the instruction word at the NIP
 */
static u32 acop_get_inst(struct pt_regs *regs)
{
	u32 inst;
	u32 __user *p;

	p = (u32 __user *)regs->nip;
	if (!access_ok(VERIFY_READ, p, sizeof(*p)))
		return 0;

	if (__get_user(inst, p))
		return 0;

	return inst;
}

/**
 * @regs: regsiters at time of interrupt
 * @address: storage address
 * @error_code: Fault code, usually the DSISR or ESR depending on
 *		processor type
 *
 * Return 0 if we are able to resolve the data storage fault that
 * results from a CT miss in the ACOP register.
 */
int acop_handle_fault(struct pt_regs *regs, unsigned long address,
		      unsigned long error_code)
{
	int ct;
	u32 inst = 0;

	if (!cpu_has_feature(CPU_FTR_ICSWX)) {
		pr_info("No coprocessors available");
		_exception(SIGILL, regs, ILL_ILLOPN, address);
	}

	if (!user_mode(regs)) {
		/* this could happen if the HV denies the
		 * kernel access, for now we just die */
		die("ICSWX from kernel failed", regs, SIGSEGV);
	}

	/* Some implementations leave us a hint for the CT */
	ct = ICSWX_GET_CT_HINT(error_code);
	if (ct < 0) {
		/* we have to peek at the instruction word to figure out CT */
		u32 ccw;
		u32 rs;

		inst = acop_get_inst(regs);
		if (inst == 0)
			return -1;

		rs = (inst >> (31 - 10)) & 0x1f;
		ccw = regs->gpr[rs];
		ct = (ccw >> 16) & 0x3f;
	}

	/*
	 * We could be here because another thread has enabled acop
	 * but the ACOP register has yet to be updated.
	 *
	 * This should have been taken care of by the IPI to sync all
	 * the threads (see smp_call_function(sync_cop, mm, 1)), but
	 * that could take forever if there are a significant amount
	 * of threads.
	 *
	 * Given the number of threads on some of these systems,
	 * perhaps this is the best way to sync ACOP rather than whack
	 * every thread with an IPI.
	 */
	if ((acop_copro_type_bit(ct) & current->active_mm->context.acop) != 0) {
		sync_cop(current->active_mm);
		return 0;
	}

	/* check for alternate policy */
	if (!acop_use_cop(ct))
		return 0;

	/* at this point the CT is unknown to the system */
	pr_warn("%s[%d]: Coprocessor %d is unavailable\n",
		current->comm, current->pid, ct);

	/* get inst if we don't already have it */
	if (inst == 0) {
		inst = acop_get_inst(regs);
		if (inst == 0)
			return -1;
	}

	/* Check if the instruction is the "record form" */
	if (inst & 1) {
		/*
		 * the instruction is "record" form so we can reject
		 * using CR0
		 */
		regs->ccr &= ~(0xful << 28);
		regs->ccr |= ICSWX_RC_NOT_FOUND << 28;

		/* Move on to the next instruction */
		regs->nip += 4;
	} else {
		/*
		 * There is no architected mechanism to report a bad
		 * CT so we could either SIGILL or report nothing.
		 * Since the non-record version should only bu used
		 * for "hints" or "don't care" we should probably do
		 * nothing.  However, I could see how some people
		 * might want an SIGILL so it here if you want it.
		 */
#ifdef CONFIG_PPC_ICSWX_USE_SIGILL
		_exception(SIGILL, regs, ILL_ILLOPN, address);
#else
		regs->nip += 4;
#endif
	}

	return 0;
}
EXPORT_SYMBOL_GPL(acop_handle_fault);