From b077ffb3b767c3efb44d00b998385a9cb127255c Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Fri, 16 Feb 2007 01:48:11 -0800 Subject: 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 Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Dave Jones --- arch/i386/lib/Makefile | 2 ++ arch/i386/lib/msr-on-cpu.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 72 insertions(+) create mode 100644 arch/i386/lib/msr-on-cpu.c (limited to 'arch/i386') diff --git a/arch/i386/lib/Makefile b/arch/i386/lib/Makefile index d86a548..0d41223 100644 --- a/arch/i386/lib/Makefile +++ b/arch/i386/lib/Makefile @@ -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 diff --git a/arch/i386/lib/msr-on-cpu.c b/arch/i386/lib/msr-on-cpu.c new file mode 100644 index 0000000..2092ea1 --- /dev/null +++ b/arch/i386/lib/msr-on-cpu.c @@ -0,0 +1,70 @@ +#include +#include +#include +#include + +#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); -- cgit v1.1