b077ffb3b7
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>
71 lines
1.2 KiB
C
71 lines
1.2 KiB
C
#include <linux/module.h>
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#include <linux/preempt.h>
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#include <linux/smp.h>
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#include <asm/msr.h>
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#ifdef CONFIG_SMP
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struct msr_info {
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u32 msr_no;
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u32 l, h;
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};
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static void __rdmsr_on_cpu(void *info)
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{
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struct msr_info *rv = info;
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rdmsr(rv->msr_no, rv->l, rv->h);
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}
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void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
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{
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preempt_disable();
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if (smp_processor_id() == cpu)
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rdmsr(msr_no, *l, *h);
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else {
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struct msr_info rv;
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rv.msr_no = msr_no;
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smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 0, 1);
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*l = rv.l;
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*h = rv.h;
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}
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preempt_enable();
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}
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static void __wrmsr_on_cpu(void *info)
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{
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struct msr_info *rv = info;
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wrmsr(rv->msr_no, rv->l, rv->h);
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}
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void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
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{
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preempt_disable();
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if (smp_processor_id() == cpu)
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wrmsr(msr_no, l, h);
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else {
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struct msr_info rv;
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rv.msr_no = msr_no;
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rv.l = l;
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rv.h = h;
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smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 0, 1);
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}
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preempt_enable();
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}
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#else
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void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
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{
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rdmsr(msr_no, *l, *h);
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}
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void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
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{
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wrmsr(msr_no, l, h);
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}
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#endif
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EXPORT_SYMBOL(rdmsr_on_cpu);
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EXPORT_SYMBOL(wrmsr_on_cpu);
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