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x86: MSR: add methods for writing of an MSR on several CPUs
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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: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
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Borislav Petkov committed Jun 10, 2009
1 parent 6bc1096 commit b034c19
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Showing 2 changed files with 104 additions and 6 deletions.
12 changes: 12 additions & 0 deletions arch/x86/include/asm/msr.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand All @@ -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)
{
Expand Down
98 changes: 92 additions & 6 deletions arch/x86/lib/msr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6,48 +6,133 @@
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)
{
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;
*h = rv.reg.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;
err = smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 1);

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. */
Expand All @@ -70,28 +155,29 @@ 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;
*h = rv.reg.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;
err = smp_call_function_single(cpu, __wrmsr_safe_on_cpu, &rv, 1);

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);

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