rdmsr_on_cpu, wrmsr_on_cpu

There was OpenVZ specific bug rendering some cpufreq drivers unusable on SMP.
In short, when cpufreq code thinks it confined itself to needed cpu by means
of set_cpus_allowed() to execute rdmsr, some "virtual cpu" feature can migrate
process to anywhere.  This triggers bugons and does wrong things in general.

This got fixed by introducing rdmsr_on_cpu and wrmsr_on_cpu executing rdmsr
and wrmsr on given physical cpu by means of smp_call_function_single().

Dave Jones mentioned cpufreq might be not only user of rdmsr_on_cpu() and
wrmsr_on_cpu(), so I'm putting them into arch/{i386,x86_64}/lib/ .

Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>
This commit is contained in:
Alexey Dobriyan 2007-02-16 01:48:11 -08:00 committed by Dave Jones
parent 22f7bb0329
commit b077ffb3b7
6 changed files with 79 additions and 1 deletions

View file

@ -7,3 +7,5 @@ lib-y = checksum.o delay.o usercopy.o getuser.o putuser.o memcpy.o strstr.o \
bitops.o semaphore.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
obj-y = msr-on-cpu.o

View file

@ -0,0 +1,70 @@
#include <linux/module.h>
#include <linux/preempt.h>
#include <linux/smp.h>
#include <asm/msr.h>
#ifdef CONFIG_SMP
struct msr_info {
u32 msr_no;
u32 l, h;
};
static void __rdmsr_on_cpu(void *info)
{
struct msr_info *rv = info;
rdmsr(rv->msr_no, rv->l, rv->h);
}
void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
{
preempt_disable();
if (smp_processor_id() == cpu)
rdmsr(msr_no, *l, *h);
else {
struct msr_info rv;
rv.msr_no = msr_no;
smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 0, 1);
*l = rv.l;
*h = rv.h;
}
preempt_enable();
}
static void __wrmsr_on_cpu(void *info)
{
struct msr_info *rv = info;
wrmsr(rv->msr_no, rv->l, rv->h);
}
void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
{
preempt_disable();
if (smp_processor_id() == cpu)
wrmsr(msr_no, l, h);
else {
struct msr_info rv;
rv.msr_no = msr_no;
rv.l = l;
rv.h = h;
smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 0, 1);
}
preempt_enable();
}
#else
void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
{
rdmsr(msr_no, *l, *h);
}
void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
{
wrmsr(msr_no, l, h);
}
#endif
EXPORT_SYMBOL(rdmsr_on_cpu);
EXPORT_SYMBOL(wrmsr_on_cpu);

View file

@ -4,7 +4,7 @@
CFLAGS_csum-partial.o := -funroll-loops
obj-y := io.o iomap_copy.o
obj-y := io.o iomap_copy.o msr-on-cpu.o
lib-y := csum-partial.o csum-copy.o csum-wrappers.o delay.o \
usercopy.o getuser.o putuser.o \

View file

@ -0,0 +1 @@
#include "../../i386/lib/msr-on-cpu.c"

View file

@ -83,6 +83,9 @@ static inline void wrmsrl (unsigned long msr, unsigned long long val)
: "c" (counter))
#endif /* !CONFIG_PARAVIRT */
void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
/* symbolic names for some interesting MSRs */
/* Intel defined MSRs. */
#define MSR_IA32_P5_MC_ADDR 0

View file

@ -160,6 +160,8 @@ static inline unsigned int cpuid_edx(unsigned int op)
#define MSR_IA32_UCODE_WRITE 0x79
#define MSR_IA32_UCODE_REV 0x8b
void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
#endif