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Commit 22085a66 authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

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: default avatarBorislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1394384725-10796-2-git-send-email-bp@alien8.de


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 2a0788dc

arch/x86/include/asm/msr.h

+2 −0
Original line number Diff line number Diff line
@@ -214,6 +214,8 @@ do { \ 


struct msr *msrs_alloc(void);

void msrs_free(struct msr *msrs);

int msr_set_bit(u32 msr, u8 bit);

int msr_clear_bit(u32 msr, u8 bit);



#ifdef CONFIG_SMP

int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);

arch/x86/lib/msr.c

+88 −1
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ struct msr *msrs_alloc(void) 


	msrs = alloc_percpu(struct msr);

	if (!msrs) {

		pr_warning("%s: error allocating msrs\n", __func__);

		pr_warn("%s: error allocating msrs\n", __func__);

		return NULL;

	}
@@ -21,3 +21,90 @@ 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);

}