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[x86_64] Add functions to read and write model-specific registers
Signed-off-by: Michael Brown <mcb30@ipxe.org>
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mcb30 committed Jul 23, 2014
1 parent 945b8de commit 5888c88
Showing 1 changed file with 43 additions and 0 deletions.
43 changes: 43 additions & 0 deletions src/arch/x86_64/include/ipxe/msr.h
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#ifndef _IPXE_MSR_H
#define _IPXE_MSR_H

/** @file
*
* Model-specific registers
*
*/

FILE_LICENCE ( GPL2_OR_LATER );

/**
* Read model-specific register
*
* @v msr Model-specific register
* @ret value Value
*/
static inline __attribute__ (( always_inline )) uint64_t
rdmsr ( unsigned int msr ) {
uint32_t high;
uint32_t low;

__asm__ __volatile__ ( "rdmsr" :
"=d" ( high ), "=a" ( low ) : "c" ( msr ) );
return ( ( ( ( uint64_t ) high ) << 32 ) | low );
}

/**
* Write model-specific register
*
* @v msr Model-specific register
* @v value Value
*/
static inline __attribute__ (( always_inline )) void
wrmsr ( unsigned int msr, uint64_t value ) {
uint32_t high = ( value >> 32 );
uint32_t low = ( value >> 0 );

__asm__ __volatile__ ( "wrmsr" : :
"c" ( msr ), "d" ( high ), "a" ( low ) );
}

#endif /* _IPXE_MSR_H */

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