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
|
From e6eac38976a1eebb792eb6a02fd95ed0868576fc Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 25 Jul 2018 14:02:38 +0200
Subject: [PATCH 212/347] arm64: fpsimd: use preemp_disable in addition to
local_bh_disable()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz
In v4.16-RT I noticed a number of warnings from task_fpsimd_load(). The
code disables BH and expects that it is not preemptible. On -RT the
task remains preemptible but remains the same CPU. This may corrupt the
content of the SIMD registers if the task is preempted during
saving/restoring those registers.
Add preempt_disable()/enable() to enfore the required semantic on -RT.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/arm64/kernel/fpsimd.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 89ab68cb35bb..481793a5adc1 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -159,6 +159,16 @@ static void sve_free(struct task_struct *task)
__sve_free(task);
}
+static void *sve_free_atomic(struct task_struct *task)
+{
+ void *sve_state = task->thread.sve_state;
+
+ WARN_ON(test_tsk_thread_flag(task, TIF_SVE));
+
+ task->thread.sve_state = NULL;
+ return sve_state;
+}
+
/*
* TIF_SVE controls whether a task can use SVE without trapping while
* in userspace, and also the way a task's FPSIMD/SVE state is stored
@@ -549,6 +559,7 @@ int sve_set_vector_length(struct task_struct *task,
* non-SVE thread.
*/
if (task == current) {
+ preempt_disable();
local_bh_disable();
fpsimd_save();
@@ -559,8 +570,10 @@ int sve_set_vector_length(struct task_struct *task,
if (test_and_clear_tsk_thread_flag(task, TIF_SVE))
sve_to_fpsimd(task);
- if (task == current)
+ if (task == current) {
local_bh_enable();
+ preempt_enable();
+ }
/*
* Force reallocation of task SVE state to the correct size
@@ -815,6 +828,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
sve_alloc(current);
+ preempt_disable();
local_bh_disable();
fpsimd_save();
@@ -828,6 +842,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
WARN_ON(1); /* SVE access shouldn't have trapped */
local_bh_enable();
+ preempt_enable();
}
/*
@@ -894,10 +909,12 @@ void fpsimd_thread_switch(struct task_struct *next)
void fpsimd_flush_thread(void)
{
int vl, supported_vl;
+ void *mem = NULL;
if (!system_supports_fpsimd())
return;
+ preempt_disable();
local_bh_disable();
memset(¤t->thread.uw.fpsimd_state, 0,
@@ -906,7 +923,7 @@ void fpsimd_flush_thread(void)
if (system_supports_sve()) {
clear_thread_flag(TIF_SVE);
- sve_free(current);
+ mem = sve_free_atomic(current);
/*
* Reset the task vector length as required.
@@ -942,6 +959,8 @@ void fpsimd_flush_thread(void)
set_thread_flag(TIF_FOREIGN_FPSTATE);
local_bh_enable();
+ preempt_enable();
+ kfree(mem);
}
/*
@@ -953,9 +972,11 @@ void fpsimd_preserve_current_state(void)
if (!system_supports_fpsimd())
return;
+ preempt_disable();
local_bh_disable();
fpsimd_save();
local_bh_enable();
+ preempt_enable();
}
/*
@@ -1026,6 +1047,7 @@ void fpsimd_restore_current_state(void)
return;
}
+ preempt_disable();
local_bh_disable();
if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
@@ -1034,6 +1056,7 @@ void fpsimd_restore_current_state(void)
}
local_bh_enable();
+ preempt_enable();
}
/*
@@ -1046,6 +1069,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state)
if (WARN_ON(!system_supports_fpsimd()))
return;
+ preempt_disable();
local_bh_disable();
current->thread.uw.fpsimd_state = *state;
@@ -1058,6 +1082,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state)
clear_thread_flag(TIF_FOREIGN_FPSTATE);
local_bh_enable();
+ preempt_enable();
}
/*
@@ -1104,6 +1129,7 @@ void kernel_neon_begin(void)
BUG_ON(!may_use_simd());
+ preempt_disable();
local_bh_disable();
__this_cpu_write(kernel_neon_busy, true);
@@ -1117,6 +1143,7 @@ void kernel_neon_begin(void)
preempt_disable();
local_bh_enable();
+ preempt_enable();
}
EXPORT_SYMBOL(kernel_neon_begin);
--
2.36.1
|
