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Commit b034c19f authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86: MSR: add methods for writing of an MSR on several CPUs 



Provide for concurrent MSR writes on all the CPUs in the cpumask. Also,
add a temporary workaround for smp_call_function_many which skips the
CPU we're executing on.

Bart: zero out rv struct which is allocated on stack.

CC: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarBorislav Petkov <borislav.petkov@amd.com>
Signed-off-by: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
parent 6bc1096d

arch/x86/include/asm/msr.h

+12 −0
Original line number Diff line number Diff line
@@ -227,6 +227,8 @@ do { \ 
#ifdef CONFIG_SMP

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

int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);

void rdmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs);

void wrmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs);

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

int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);

#else  /*  CONFIG_SMP  */
@@ -240,6 +242,16 @@ static inline int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h) 
	wrmsr(msr_no, l, h);

	return 0;

}

static inline void rdmsr_on_cpus(const cpumask_t *m, u32 msr_no,

				struct msr *msrs)

{

       rdmsr_on_cpu(0, msr_no, &(msrs[0].l), &(msrs[0].h));

}

static inline void wrmsr_on_cpus(const cpumask_t *m, u32 msr_no,

				struct msr *msrs)

{

       wrmsr_on_cpu(0, msr_no, msrs[0].l, msrs[0].h);

}

static inline int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no,

				    u32 *l, u32 *h)

{

arch/x86/lib/msr.c

+92 −6
Original line number Diff line number Diff line
@@ -6,21 +6,37 @@ 
struct msr_info {

	u32 msr_no;

	struct msr reg;

	struct msr *msrs;

	int off;

	int err;

};



static void __rdmsr_on_cpu(void *info)

{

	struct msr_info *rv = info;

	struct msr *reg;

	int this_cpu = raw_smp_processor_id();



	rdmsr(rv->msr_no, rv->reg.l, rv->reg.h);

	if (rv->msrs)

		reg = &rv->msrs[this_cpu - rv->off];

	else

		reg = &rv->reg;



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

}



static void __wrmsr_on_cpu(void *info)

{

	struct msr_info *rv = info;

	struct msr *reg;

	int this_cpu = raw_smp_processor_id();



	if (rv->msrs)

		reg = &rv->msrs[this_cpu - rv->off];

	else

		reg = &rv->reg;



	wrmsr(rv->msr_no, rv->reg.l, rv->reg.h);

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

}



int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
@@ -28,6 +44,8 @@ int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h) 
	int err;

	struct msr_info rv;



	memset(&rv, 0, sizeof(rv));



	rv.msr_no = msr_no;

	err = smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 1);

	*l = rv.reg.l;
@@ -35,12 +53,15 @@ int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h) 


	return err;

}

EXPORT_SYMBOL(rdmsr_on_cpu);



int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)

{

	int err;

	struct msr_info rv;



	memset(&rv, 0, sizeof(rv));



	rv.msr_no = msr_no;

	rv.reg.l = l;

	rv.reg.h = h;
@@ -48,6 +69,70 @@ int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h) 


	return err;

}

EXPORT_SYMBOL(wrmsr_on_cpu);



/* rdmsr on a bunch of CPUs

 *

 * @mask:       which CPUs

 * @msr_no:     which MSR

 * @msrs:       array of MSR values

 *

 */

void rdmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs)

{

	struct msr_info rv;

	int this_cpu;



	memset(&rv, 0, sizeof(rv));



	rv.off    = cpumask_first(mask);

	rv.msrs	  = msrs;

	rv.msr_no = msr_no;



	preempt_disable();

	/*

	 * FIXME: handle the CPU we're executing on separately for now until

	 * smp_call_function_many has been fixed to not skip it.

	 */

	this_cpu = raw_smp_processor_id();

	smp_call_function_single(this_cpu, __rdmsr_on_cpu, &rv, 1);



	smp_call_function_many(mask, __rdmsr_on_cpu, &rv, 1);

	preempt_enable();

}

EXPORT_SYMBOL(rdmsr_on_cpus);



/*

 * wrmsr on a bunch of CPUs

 *

 * @mask:       which CPUs

 * @msr_no:     which MSR

 * @msrs:       array of MSR values

 *

 */

void wrmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs)

{

	struct msr_info rv;

	int this_cpu;



	memset(&rv, 0, sizeof(rv));



	rv.off    = cpumask_first(mask);

	rv.msrs   = msrs;

	rv.msr_no = msr_no;



	preempt_disable();

	/*

	 * FIXME: handle the CPU we're executing on separately for now until

	 * smp_call_function_many has been fixed to not skip it.

	 */

	this_cpu = raw_smp_processor_id();

	smp_call_function_single(this_cpu, __wrmsr_on_cpu, &rv, 1);



	smp_call_function_many(mask, __wrmsr_on_cpu, &rv, 1);

	preempt_enable();

}

EXPORT_SYMBOL(wrmsr_on_cpus);



/* These "safe" variants are slower and should be used when the target MSR

   may not actually exist. */
@@ -70,6 +155,8 @@ int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h) 
	int err;

	struct msr_info rv;



	memset(&rv, 0, sizeof(rv));



	rv.msr_no = msr_no;

	err = smp_call_function_single(cpu, __rdmsr_safe_on_cpu, &rv, 1);

	*l = rv.reg.l;
@@ -77,12 +164,15 @@ int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h) 


	return err ? err : rv.err;

}

EXPORT_SYMBOL(rdmsr_safe_on_cpu);



int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)

{

	int err;

	struct msr_info rv;



	memset(&rv, 0, sizeof(rv));



	rv.msr_no = msr_no;

	rv.reg.l = l;

	rv.reg.h = h;
@@ -90,8 +180,4 @@ int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h) 


	return err ? err : rv.err;

}



EXPORT_SYMBOL(rdmsr_on_cpu);

EXPORT_SYMBOL(wrmsr_on_cpu);

EXPORT_SYMBOL(rdmsr_safe_on_cpu);

EXPORT_SYMBOL(wrmsr_safe_on_cpu);