1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_BARRIER_H
3 #define _ASM_X86_BARRIER_H
4
5 #include <asm/alternative.h>
6 #include <asm/nops.h>
7
8 /*
9 * Force strict CPU ordering.
10 * And yes, this might be required on UP too when we're talking
11 * to devices.
12 */
13
14 #ifdef CONFIG_X86_32
15 #define mb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "mfence", \
16 X86_FEATURE_XMM2) ::: "memory", "cc")
17 #define rmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "lfence", \
18 X86_FEATURE_XMM2) ::: "memory", "cc")
19 #define wmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "sfence", \
20 X86_FEATURE_XMM2) ::: "memory", "cc")
21 #else
22 #define __mb() asm volatile("mfence":::"memory")
23 #define __rmb() asm volatile("lfence":::"memory")
24 #define __wmb() asm volatile("sfence" ::: "memory")
25 #endif
26
27 /**
28 * array_index_mask_nospec() - generate a mask that is ~0UL when the
29 * bounds check succeeds and 0 otherwise
30 * @index: array element index
31 * @size: number of elements in array
32 *
33 * Returns:
34 * 0 - (index < size)
35 */
array_index_mask_nospec(unsigned long index,unsigned long size)36 static inline unsigned long array_index_mask_nospec(unsigned long index,
37 unsigned long size)
38 {
39 unsigned long mask;
40
41 asm volatile ("cmp %1,%2; sbb %0,%0;"
42 :"=r" (mask)
43 :"g"(size),"r" (index)
44 :"cc");
45 return mask;
46 }
47
48 /* Override the default implementation from linux/nospec.h. */
49 #define array_index_mask_nospec array_index_mask_nospec
50
51 /* Prevent speculative execution past this barrier. */
52 #define barrier_nospec() alternative("", "lfence", X86_FEATURE_LFENCE_RDTSC)
53
54 #define __dma_rmb() barrier()
55 #define __dma_wmb() barrier()
56
57 #define __smp_mb() asm volatile("lock; addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")
58
59 #define __smp_rmb() dma_rmb()
60 #define __smp_wmb() barrier()
61 #define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)
62
63 #define __smp_store_release(p, v) \
64 do { \
65 compiletime_assert_atomic_type(*p); \
66 barrier(); \
67 WRITE_ONCE(*p, v); \
68 } while (0)
69
70 #define __smp_load_acquire(p) \
71 ({ \
72 typeof(*p) ___p1 = READ_ONCE(*p); \
73 compiletime_assert_atomic_type(*p); \
74 barrier(); \
75 ___p1; \
76 })
77
78 /* Atomic operations are already serializing on x86 */
79 #define __smp_mb__before_atomic() do { } while (0)
80 #define __smp_mb__after_atomic() do { } while (0)
81
82 #include <asm-generic/barrier.h>
83
84 /*
85 * Make previous memory operations globally visible before
86 * a WRMSR.
87 *
88 * MFENCE makes writes visible, but only affects load/store
89 * instructions. WRMSR is unfortunately not a load/store
90 * instruction and is unaffected by MFENCE. The LFENCE ensures
91 * that the WRMSR is not reordered.
92 *
93 * Most WRMSRs are full serializing instructions themselves and
94 * do not require this barrier. This is only required for the
95 * IA32_TSC_DEADLINE and X2APIC MSRs.
96 */
weak_wrmsr_fence(void)97 static inline void weak_wrmsr_fence(void)
98 {
99 asm volatile("mfence; lfence" : : : "memory");
100 }
101
102 #endif /* _ASM_X86_BARRIER_H */
103