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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>
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parent
22f7bb0329
commit
b077ffb3b7
6 changed files with 79 additions and 1 deletions
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@ -7,3 +7,5 @@ lib-y = checksum.o delay.o usercopy.o getuser.o putuser.o memcpy.o strstr.o \
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bitops.o semaphore.o
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bitops.o semaphore.o
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lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
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lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
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obj-y = msr-on-cpu.o
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70
arch/i386/lib/msr-on-cpu.c
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70
arch/i386/lib/msr-on-cpu.c
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@ -0,0 +1,70 @@
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#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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@ -4,7 +4,7 @@
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CFLAGS_csum-partial.o := -funroll-loops
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CFLAGS_csum-partial.o := -funroll-loops
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obj-y := io.o iomap_copy.o
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obj-y := io.o iomap_copy.o msr-on-cpu.o
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lib-y := csum-partial.o csum-copy.o csum-wrappers.o delay.o \
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lib-y := csum-partial.o csum-copy.o csum-wrappers.o delay.o \
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usercopy.o getuser.o putuser.o \
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usercopy.o getuser.o putuser.o \
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1
arch/x86_64/lib/msr-on-cpu.c
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1
arch/x86_64/lib/msr-on-cpu.c
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@ -0,0 +1 @@
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#include "../../i386/lib/msr-on-cpu.c"
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@ -83,6 +83,9 @@ static inline void wrmsrl (unsigned long msr, unsigned long long val)
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: "c" (counter))
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: "c" (counter))
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#endif /* !CONFIG_PARAVIRT */
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#endif /* !CONFIG_PARAVIRT */
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void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
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void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
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/* symbolic names for some interesting MSRs */
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/* symbolic names for some interesting MSRs */
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/* Intel defined MSRs. */
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/* Intel defined MSRs. */
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#define MSR_IA32_P5_MC_ADDR 0
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#define MSR_IA32_P5_MC_ADDR 0
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@ -160,6 +160,8 @@ static inline unsigned int cpuid_edx(unsigned int op)
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#define MSR_IA32_UCODE_WRITE 0x79
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#define MSR_IA32_UCODE_WRITE 0x79
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#define MSR_IA32_UCODE_REV 0x8b
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#define MSR_IA32_UCODE_REV 0x8b
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void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
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void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
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#endif
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#endif
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