Commit b077ffb3 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Dave Jones
Browse files

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: default avatarAlexey Dobriyan <adobriyan@openvz.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 22f7bb03

arch/i386/lib/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -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

arch/i386/lib/msr-on-cpu.c

0 → 100644
+70 −0
Original line number Diff line number Diff line 
#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);

arch/x86_64/lib/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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  \

arch/x86_64/lib/msr-on-cpu.c

0 → 100644
+1 −0
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#include "../../i386/lib/msr-on-cpu.c"

include/asm-i386/msr.h

+3 −0
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@@ -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

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