arch/um/sys-i386/shared/sysdep/system.h

   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  */
 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