1 #ifndef _ASM_X86_SYSTEM_H_
2 #define _ASM_X86_SYSTEM_H_
3
4 #include <asm/asm.h>
5 #include <asm/segment.h>
6 #include <asm/cpufeature.h>
7 #include <asm/cmpxchg.h>
8 #include <asm/nops.h>
9
10 #include <linux/kernel.h>
11 #include <linux/irqflags.h>
12
13 /* entries in ARCH_DLINFO: */
14 #ifdef CONFIG_IA32_EMULATION
15 # define AT_VECTOR_SIZE_ARCH 2
16 #else
17 # define AT_VECTOR_SIZE_ARCH 1
18 #endif
19
20 extern unsigned long arch_align_stack(unsigned long sp);
21
22 void default_idle(void);
23
24 /*
25 * Force strict CPU ordering.
26 * And yes, this is required on UP too when we're talking
27 * to devices.
28 */
29 #ifdef CONFIG_X86_32
30 /*
31 * Some non-Intel clones support out of order store. wmb() ceases to be a
32 * nop for these.
33 */
34 #define mb() alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
35 #define rmb() alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
36 #define wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
37 #else
38 #define mb() asm volatile("mfence":::"memory")
39 #define rmb() asm volatile("lfence":::"memory")
40 #define wmb() asm volatile("sfence" ::: "memory")
41 #endif
42
43 /**
44 * read_barrier_depends - Flush all pending reads that subsequents reads
45 * depend on.
46 *
47 * No data-dependent reads from memory-like regions are ever reordered
48 * over this barrier. All reads preceding this primitive are guaranteed
49 * to access memory (but not necessarily other CPUs' caches) before any
50 * reads following this primitive that depend on the data return by
51 * any of the preceding reads. This primitive is much lighter weight than
52 * rmb() on most CPUs, and is never heavier weight than is
53 * rmb().
54 *
55 * These ordering constraints are respected by both the local CPU
56 * and the compiler.
57 *
58 * Ordering is not guaranteed by anything other than these primitives,
59 * not even by data dependencies. See the documentation for
60 * memory_barrier() for examples and URLs to more information.
61 *
62 * For example, the following code would force ordering (the initial
63 * value of "a" is zero, "b" is one, and "p" is "&a"):
64 *
65 * <programlisting>
66 * CPU 0 CPU 1
67 *
68 * b = 2;
69 * memory_barrier();
70 * p = &b; q = p;
71 * read_barrier_depends();
72 * d = *q;
73 * </programlisting>
74 *
75 * because the read of "*q" depends on the read of "p" and these
76 * two reads are separated by a read_barrier_depends(). However,
77 * the following code, with the same initial values for "a" and "b":
78 *
79 * <programlisting>
80 * CPU 0 CPU 1
81 *
82 * a = 2;
83 * memory_barrier();
84 * b = 3; y = b;
85 * read_barrier_depends();
86 * x = a;
87 * </programlisting>
88 *
89 * does not enforce ordering, since there is no data dependency between
90 * the read of "a" and the read of "b". Therefore, on some CPUs, such
91 * as Alpha, "y" could be set to 3 and "x" to 0. Use rmb()
92 * in cases like this where there are no data dependencies.
93 **/
94
95 #define read_barrier_depends() do { } while (0)
96
97 #ifdef CONFIG_SMP
98 #define smp_mb() mb()
99 #ifdef CONFIG_X86_PPRO_FENCE
100 # define smp_rmb() rmb()
101 #else
102 # define smp_rmb() barrier()
103 #endif
104 #ifdef CONFIG_X86_OOSTORE
105 # define smp_wmb() wmb()
106 #else
107 # define smp_wmb() barrier()
108 #endif
109 #define smp_read_barrier_depends() read_barrier_depends()
110 #define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
111 #else
112 #define smp_mb() barrier()
113 #define smp_rmb() barrier()
114 #define smp_wmb() barrier()
115 #define smp_read_barrier_depends() do { } while (0)
116 #define set_mb(var, value) do { var = value; barrier(); } while (0)
117 #endif
118
119 /*
120 * Stop RDTSC speculation. This is needed when you need to use RDTSC
121 * (or get_cycles or vread that possibly accesses the TSC) in a defined
122 * code region.
123 *
124 * (Could use an alternative three way for this if there was one.)
125 */
rdtsc_barrier(void)126 static inline void rdtsc_barrier(void)
127 {
128 alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
129 alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
130 }
131
132 #endif
133