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
|
/*
* 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 "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_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);
|
