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msr-on-cpu.c

#include <linux/module.h>
#include <linux/preempt.h>
#include <linux/smp.h>
#include <asm/msr.h>

struct msr_info {
      u32 msr_no;
      u32 l, h;
      int err;
};

static void __rdmsr_on_cpu(void *info)
{
      struct msr_info *rv = info;

      rdmsr(rv->msr_no, rv->l, rv->h);
}

static void __rdmsr_safe_on_cpu(void *info)
{
      struct msr_info *rv = info;

      rv->err = rdmsr_safe(rv->msr_no, &rv->l, &rv->h);
}

static int _rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h, int safe)
{
      int err = 0;
      struct msr_info rv;

      rv.msr_no = msr_no;
      if (safe) {
            smp_call_function_single(cpu, __rdmsr_safe_on_cpu, &rv, 0, 1);
            err = rv.err;
      } else {
            smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 0, 1);
      }
      *l = rv.l;
      *h = rv.h;

      return err;
}

static void __wrmsr_on_cpu(void *info)
{
      struct msr_info *rv = info;

      wrmsr(rv->msr_no, rv->l, rv->h);
}

static void __wrmsr_safe_on_cpu(void *info)
{
      struct msr_info *rv = info;

      rv->err = wrmsr_safe(rv->msr_no, rv->l, rv->h);
}

static int _wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h, int safe)
{
      int err = 0;
      struct msr_info rv;

      rv.msr_no = msr_no;
      rv.l = l;
      rv.h = h;
      if (safe) {
            smp_call_function_single(cpu, __wrmsr_safe_on_cpu, &rv, 0, 1);
            err = rv.err;
      } else {
            smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 0, 1);
      }

      return err;
}

void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
{
      _wrmsr_on_cpu(cpu, msr_no, l, h, 0);
}

void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
{
      _rdmsr_on_cpu(cpu, msr_no, l, h, 0);
}

/* These "safe" variants are slower and should be used when the target MSR
   may not actually exist. */
int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
{
      return _wrmsr_on_cpu(cpu, msr_no, l, h, 1);
}

int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
{
      return _rdmsr_on_cpu(cpu, msr_no, l, h, 1);
}

EXPORT_SYMBOL(rdmsr_on_cpu);
EXPORT_SYMBOL(wrmsr_on_cpu);
EXPORT_SYMBOL(rdmsr_safe_on_cpu);
EXPORT_SYMBOL(wrmsr_safe_on_cpu);

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