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    Subject[PATCH x86 for review II] [21/39] i386: rdmsr_on_cpu, wrmsr_on_cpu
    Date

    From: Alexey Dobriyan <adobriyan@openvz.org>
    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().

    AK: link it into 64bit kernel too because cpufreq drivers use it.

    arch/i386/kernel/cpu/cpufreq/p4-clockmod.c | 30 ++----------
    arch/i386/lib/Makefile | 2
    arch/i386/kernel/cpu/cpufreq/p4-clockmod.c | 30 ++----------
    arch/i386/lib/Makefile | 2
    arch/i386/lib/msr-on-cpu.c | 70 +++++++++++++++++++++++++++++
    arch/x86_64/lib/Makefile | 4 +
    include/asm-i386/msr.h | 3 +
    5 files changed, 84 insertions(+), 25 deletions(-)

    Signed-off-by: Andi Kleen <ak@suse.de>

    Index: linux/arch/i386/lib/Makefile
    ===================================================================
    --- linux.orig/arch/i386/lib/Makefile
    +++ linux/arch/i386/lib/Makefile
    @@ -7,3 +7,5 @@ lib-y = checksum.o delay.o usercopy.o ge
    bitops.o semaphore.o

    lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
    +
    +obj-y = msr-on-cpu.o
    Index: linux/arch/i386/lib/msr-on-cpu.c
    ===================================================================
    --- /dev/null
    +++ linux/arch/i386/lib/msr-on-cpu.c
    @@ -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);
    Index: linux/include/asm-i386/msr.h
    ===================================================================
    --- linux.orig/include/asm-i386/msr.h
    +++ linux/include/asm-i386/msr.h
    @@ -83,6 +83,9 @@ static inline void wrmsrl (unsigned long
    : "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
    Index: linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
    ===================================================================
    --- linux.orig/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
    +++ linux/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
    @@ -62,7 +62,7 @@ static int cpufreq_p4_setdc(unsigned int
    if (!cpu_online(cpu) || (newstate > DC_DISABLE) || (newstate == DC_RESV))
    return -EINVAL;

    - rdmsr(MSR_IA32_THERM_STATUS, l, h);
    + rdmsr_on_cpu(cpu, MSR_IA32_THERM_STATUS, &l, &h);

    if (l & 0x01)
    dprintk("CPU#%d currently thermal throttled\n", cpu);
    @@ -70,10 +70,10 @@ static int cpufreq_p4_setdc(unsigned int
    if (has_N44_O17_errata[cpu] && (newstate == DC_25PT || newstate == DC_DFLT))
    newstate = DC_38PT;

    - rdmsr(MSR_IA32_THERM_CONTROL, l, h);
    + rdmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, &l, &h);
    if (newstate == DC_DISABLE) {
    dprintk("CPU#%d disabling modulation\n", cpu);
    - wrmsr(MSR_IA32_THERM_CONTROL, l & ~(1<<4), h);
    + wrmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, l & ~(1<<4), h);
    } else {
    dprintk("CPU#%d setting duty cycle to %d%%\n",
    cpu, ((125 * newstate) / 10));
    @@ -84,7 +84,7 @@ static int cpufreq_p4_setdc(unsigned int
    */
    l = (l & ~14);
    l = l | (1<<4) | ((newstate & 0x7)<<1);
    - wrmsr(MSR_IA32_THERM_CONTROL, l, h);
    + wrmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, l, h);
    }

    return 0;
    @@ -111,7 +111,6 @@ static int cpufreq_p4_target(struct cpuf
    {
    unsigned int newstate = DC_RESV;
    struct cpufreq_freqs freqs;
    - cpumask_t cpus_allowed;
    int i;

    if (cpufreq_frequency_table_target(policy, &p4clockmod_table[0], target_freq, relation, &newstate))
    @@ -132,17 +131,8 @@ static int cpufreq_p4_target(struct cpuf
    /* run on each logical CPU, see section 13.15.3 of IA32 Intel Architecture Software
    * Developer's Manual, Volume 3
    */
    - cpus_allowed = current->cpus_allowed;
    -
    - for_each_cpu_mask(i, policy->cpus) {
    - cpumask_t this_cpu = cpumask_of_cpu(i);
    -
    - set_cpus_allowed(current, this_cpu);
    - BUG_ON(smp_processor_id() != i);
    -
    + for_each_cpu_mask(i, policy->cpus)
    cpufreq_p4_setdc(i, p4clockmod_table[newstate].index);
    - }
    - set_cpus_allowed(current, cpus_allowed);

    /* notifiers */
    for_each_cpu_mask(i, policy->cpus) {
    @@ -256,17 +246,9 @@ static int cpufreq_p4_cpu_exit(struct cp

    static unsigned int cpufreq_p4_get(unsigned int cpu)
    {
    - cpumask_t cpus_allowed;
    u32 l, h;

    - cpus_allowed = current->cpus_allowed;
    -
    - set_cpus_allowed(current, cpumask_of_cpu(cpu));
    - BUG_ON(smp_processor_id() != cpu);
    -
    - rdmsr(MSR_IA32_THERM_CONTROL, l, h);
    -
    - set_cpus_allowed(current, cpus_allowed);
    + rdmsr_on_cpu(cpu, MSR_IA32_THERM_CONTROL, &l, &h);

    if (l & 0x10) {
    l = l >> 1;
    Index: linux/arch/x86_64/lib/Makefile
    ===================================================================
    --- linux.orig/arch/x86_64/lib/Makefile
    +++ linux/arch/x86_64/lib/Makefile
    @@ -4,10 +4,12 @@

    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 \
    thunk.o clear_page.o copy_page.o bitstr.o bitops.o
    lib-y += memcpy.o memmove.o memset.o copy_user.o rwlock.o copy_user_nocache.o
    lib-y += memcpy_uncached_read.o
    +
    +msr-on-cpu-y += ../../i386/lib/msr-on-cpu.o
    -
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