1#include <linux/module.h>
2#include <linux/preempt.h>
3#include <asm/msr.h>
4
5struct msr *msrs_alloc(void)
6{
7	struct msr *msrs = NULL;
8
9	msrs = alloc_percpu(struct msr);
10	if (!msrs) {
11		pr_warn("%s: error allocating msrs\n", __func__);
12		return NULL;
13	}
14
15	return msrs;
16}
17EXPORT_SYMBOL(msrs_alloc);
18
19void msrs_free(struct msr *msrs)
20{
21	free_percpu(msrs);
22}
23EXPORT_SYMBOL(msrs_free);
24
25/**
26 * Read an MSR with error handling
27 *
28 * @msr: MSR to read
29 * @m: value to read into
30 *
31 * It returns read data only on success, otherwise it doesn't change the output
32 * argument @m.
33 *
34 */
35int msr_read(u32 msr, struct msr *m)
36{
37	int err;
38	u64 val;
39
40	err = rdmsrl_safe(msr, &val);
41	if (!err)
42		m->q = val;
43
44	return err;
45}
46
47/**
48 * Write an MSR with error handling
49 *
50 * @msr: MSR to write
51 * @m: value to write
52 */
53int msr_write(u32 msr, struct msr *m)
54{
55	return wrmsrl_safe(msr, m->q);
56}
57
58static inline int __flip_bit(u32 msr, u8 bit, bool set)
59{
60	struct msr m, m1;
61	int err = -EINVAL;
62
63	if (bit > 63)
64		return err;
65
66	err = msr_read(msr, &m);
67	if (err)
68		return err;
69
70	m1 = m;
71	if (set)
72		m1.q |=  BIT_64(bit);
73	else
74		m1.q &= ~BIT_64(bit);
75
76	if (m1.q == m.q)
77		return 0;
78
79	err = msr_write(msr, &m1);
80	if (err)
81		return err;
82
83	return 1;
84}
85
86/**
87 * Set @bit in a MSR @msr.
88 *
89 * Retval:
90 * < 0: An error was encountered.
91 * = 0: Bit was already set.
92 * > 0: Hardware accepted the MSR write.
93 */
94int msr_set_bit(u32 msr, u8 bit)
95{
96	return __flip_bit(msr, bit, true);
97}
98
99/**
100 * Clear @bit in a MSR @msr.
101 *
102 * Retval:
103 * < 0: An error was encountered.
104 * = 0: Bit was already cleared.
105 * > 0: Hardware accepted the MSR write.
106 */
107int msr_clear_bit(u32 msr, u8 bit)
108{
109	return __flip_bit(msr, bit, false);
110}
111