arch/x86/lib/msr.c

   1 #include <linux/module.h>
   2 #include <linux/preempt.h>
   3 #include <asm/msr.h>
   4
   5 struct 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 }
  17 EXPORT_SYMBOL(msrs_alloc);
  18
  19 void msrs_free(struct msr *msrs)
  20 {
  21         free_percpu(msrs);
  22 }
  23 EXPORT_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  */
  35 int 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  */
  53 int msr_write(u32 msr, struct msr *m)
  54 {
  55         return wrmsrl_safe(msr, m->q);
  56 }
  57
  58 static 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  */
  94 int 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  */
 107 int msr_clear_bit(u32 msr, u8 bit)
 108 {
 109         return __flip_bit(msr, bit, false);
 110 }