linux/arch/x86/lib/msr.c
Borislav Petkov 22085a66c2 x86: Add another set of MSR accessor functions
We very often need to set or clear a bit in an MSR as a result of doing
some sort of a hardware configuration. Add generic versions of that
repeated functionality in order to save us a bunch of duplicated code in
the early CPU vendor detection/config code.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1394384725-10796-2-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2014-03-13 15:34:45 -07:00

111 lines
1.6 KiB
C

#include <linux/module.h>
#include <linux/preempt.h>
#include <asm/msr.h>
struct msr *msrs_alloc(void)
{
struct msr *msrs = NULL;
msrs = alloc_percpu(struct msr);
if (!msrs) {
pr_warn("%s: error allocating msrs\n", __func__);
return NULL;
}
return msrs;
}
EXPORT_SYMBOL(msrs_alloc);
void msrs_free(struct msr *msrs)
{
free_percpu(msrs);
}
EXPORT_SYMBOL(msrs_free);
/**
* Read an MSR with error handling
*
* @msr: MSR to read
* @m: value to read into
*
* It returns read data only on success, otherwise it doesn't change the output
* argument @m.
*
*/
int msr_read(u32 msr, struct msr *m)
{
int err;
u64 val;
err = rdmsrl_safe(msr, &val);
if (!err)
m->q = val;
return err;
}
/**
* Write an MSR with error handling
*
* @msr: MSR to write
* @m: value to write
*/
int msr_write(u32 msr, struct msr *m)
{
return wrmsrl_safe(msr, m->q);
}
static inline int __flip_bit(u32 msr, u8 bit, bool set)
{
struct msr m, m1;
int err = -EINVAL;
if (bit > 63)
return err;
err = msr_read(msr, &m);
if (err)
return err;
m1 = m;
if (set)
m1.q |= BIT_64(bit);
else
m1.q &= ~BIT_64(bit);
if (m1.q == m.q)
return 0;
err = msr_write(msr, &m);
if (err)
return err;
return 1;
}
/**
* Set @bit in a MSR @msr.
*
* Retval:
* < 0: An error was encountered.
* = 0: Bit was already set.
* > 0: Hardware accepted the MSR write.
*/
int msr_set_bit(u32 msr, u8 bit)
{
return __flip_bit(msr, bit, true);
}
/**
* Clear @bit in a MSR @msr.
*
* Retval:
* < 0: An error was encountered.
* = 0: Bit was already cleared.
* > 0: Hardware accepted the MSR write.
*/
int msr_clear_bit(u32 msr, u8 bit)
{
return __flip_bit(msr, bit, false);
}