Re: [PATCH 6/6] mce-inject: use injected mce only during fakedhandler call

[Huang Ying]

This is another example for you to use my idea, implement it in a
similar way and send it out as your own.

Best Regards,
Huang Ying

On Mon, 2009-10-05 at 11:10 +0800, Hidetoshi Seto wrote: 
> In the current implementation, injected MCE is valid from the point
> the MCE is injected to the point the MCE is processed by the faked
> handler call.
> 
> This has an undesired side-effect: it is possible for it to be
> consumed by real machine_check_poll. This may confuse a real system
> error and may confuse the mce test suite.
> 
> To fix this, this patch introduces struct mce_fake_banks to hold
> injected data and a flag which indicates that the injected data is
> ready for the handler.
> 
> The mce_fake_banks.valid becomes 1 only during faked MCE handler call
> and protected by IRQ disabling. This make it impossible for real
> machine_check_poll to consume it.
> 
> (I suppose that in the near future the mce_fake_banks will be patched
>  to support injecting multiple errors on a cpu.)
> 
> Reported-by: Huang Ying <ying.huang@xxxxxxxxx>
> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/mce.h              |   12 +++++++++++-
>  arch/x86/kernel/cpu/mcheck/mce-inject.c |   25 ++++++++++++++++++++-----
>  arch/x86/kernel/cpu/mcheck/mce.c        |   16 +++++++++-------
>  3 files changed, 40 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
> index d051abd..2f1c0ef 100644
> --- a/arch/x86/include/asm/mce.h
> +++ b/arch/x86/include/asm/mce.h
> @@ -192,7 +192,6 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
>  int mce_notify_irq(void);
>  void mce_notify_process(void);
>  
> -DECLARE_PER_CPU(struct mce, injectm);
>  extern struct file_operations mce_chrdev_ops;
>  
>  /*
> @@ -218,5 +217,16 @@ void intel_init_thermal(struct cpuinfo_x86 *c);
>  
>  void mce_log_therm_throt_event(__u64 status);
>  
> +/*
> + * For error injection
> + */
> +
> +struct mce_fake_banks {
> +	int valid;
> +	struct mce injectm;
> +};
> +
> +DECLARE_PER_CPU(struct mce_fake_banks, mce_fake_banks);
> +
>  #endif /* __KERNEL__ */
>  #endif /* _ASM_X86_MCE_H */
> diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> index 4fb5b78..a481291 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> @@ -28,7 +28,7 @@
>  /* Update fake mce registers on current CPU. */
>  static void inject_mce(struct mce *m)
>  {
> -	struct mce *i = &per_cpu(injectm, m->extcpu);
> +	struct mce *i = &per_cpu(mce_fake_banks, m->extcpu).injectm;
>  
>  	/* Make sure noone reads partially written injectm */
>  	i->finished = 0;
> @@ -50,8 +50,11 @@ static void raise_poll(struct mce *m)
>  	mce_banks_t b;
>  
>  	memset(&b, 0xff, sizeof(mce_banks_t));
> +
>  	local_irq_save(flags);
> +	__get_cpu_var(mce_fake_banks).valid = 1;
>  	machine_check_poll(0, &b);
> +	__get_cpu_var(mce_fake_banks).valid = 0;
>  	local_irq_restore(flags);
>  	m->finished = 0;
>  }
> @@ -67,9 +70,12 @@ static void raise_exception(struct mce *m, struct pt_regs *pregs)
>  		regs.cs = m->cs;
>  		pregs = &regs;
>  	}
> +
>  	/* in mcheck exeception handler, irq will be disabled */
>  	local_irq_save(flags);
> +	__get_cpu_var(mce_fake_banks).valid = 1;
>  	do_machine_check(pregs, 0);
> +	__get_cpu_var(mce_fake_banks).valid = 0;
>  	local_irq_restore(flags);
>  	m->finished = 0;
>  }
> @@ -81,14 +87,20 @@ static int mce_raise_notify(struct notifier_block *self,
>  {
>  	struct die_args *args = (struct die_args *)data;
>  	int cpu = smp_processor_id();
> -	struct mce *m = &__get_cpu_var(injectm);
> +	struct mce *m = &__get_cpu_var(mce_fake_banks).injectm;
> +
>  	if (val != DIE_NMI_IPI || !cpu_isset(cpu, mce_inject_cpumask))
>  		return NOTIFY_DONE;
>  	cpu_clear(cpu, mce_inject_cpumask);
> +
> +	if (!m->finished)
> +		return NOTIFY_STOP;
> +
>  	if (m->inject_flags & MCE_INJ_EXCEPTION)
>  		raise_exception(m, args->regs);
>  	else
>  		raise_poll(m);
> +
>  	return NOTIFY_STOP;
>  }
>  
> @@ -100,11 +112,14 @@ static struct notifier_block mce_raise_nb = {
>  /* Inject mce on current CPU */
>  static int raise_local(void)
>  {
> -	struct mce *m = &__get_cpu_var(injectm);
> +	struct mce *m = &__get_cpu_var(mce_fake_banks).injectm;
>  	int context = MCE_INJ_CTX(m->inject_flags);
>  	int ret = 0;
>  	int cpu = m->extcpu;
>  
> +	if (!m->finished)
> +		return 0;
> +
>  	if (m->inject_flags & MCE_INJ_EXCEPTION) {
>  		printk(KERN_INFO "Triggering MCE exception on CPU %d\n", cpu);
>  		switch (context) {
> @@ -149,8 +164,8 @@ static void raise_mce(struct mce *m)
>  		mce_inject_cpumask = cpu_online_map;
>  		cpu_clear(get_cpu(), mce_inject_cpumask);
>  		for_each_online_cpu(cpu) {
> -			struct mce *mcpu = &per_cpu(injectm, cpu);
> -			if (!mcpu->finished || MCE_INJ_CTX(mcpu->inject_flags)
> +			struct mce *m = &per_cpu(mce_fake_banks, cpu).injectm;
> +			if (!m->finished || MCE_INJ_CTX(m->inject_flags)
>  							!= MCE_INJ_CTX_RANDOM)
>  				cpu_clear(cpu, mce_inject_cpumask);
>  		}
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 413aba8..a6d5d4a 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -110,8 +110,8 @@ void mce_setup(struct mce *m)
>  	rdmsrl(MSR_IA32_MCG_CAP, m->mcgcap);
>  }
>  
> -DEFINE_PER_CPU(struct mce, injectm);
> -EXPORT_PER_CPU_SYMBOL_GPL(injectm);
> +DEFINE_PER_CPU(struct mce_fake_banks, mce_fake_banks);
> +EXPORT_PER_CPU_SYMBOL_GPL(mce_fake_banks);
>  
>  /*
>   * Lockless MCE logging infrastructure.
> @@ -284,7 +284,7 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
>  
>  static int msr_to_offset(u32 msr)
>  {
> -	unsigned bank = __get_cpu_var(injectm.bank);
> +	unsigned bank = __get_cpu_var(mce_fake_banks).injectm.bank;
>  	if (msr == rip_msr)
>  		return offsetof(struct mce, ip);
>  	if (msr == MSR_IA32_MCx_STATUS(bank))
> @@ -303,12 +303,13 @@ static u64 mce_rdmsrl(u32 msr)
>  {
>  	u64 v;
>  
> -	if (__get_cpu_var(injectm).finished) {
> +	if (__get_cpu_var(mce_fake_banks).valid) {
>  		int offset = msr_to_offset(msr);
> +		char *m = (char *)&__get_cpu_var(mce_fake_banks).injectm;
>  
>  		if (offset < 0)
>  			return 0;
> -		return *(u64 *)((char *)&__get_cpu_var(injectm) + offset);
> +		return *(u64 *)(m + offset);
>  	}
>  
>  	if (rdmsrl_safe(msr, &v)) {
> @@ -326,11 +327,12 @@ static u64 mce_rdmsrl(u32 msr)
>  
>  static void mce_wrmsrl(u32 msr, u64 v)
>  {
> -	if (__get_cpu_var(injectm).finished) {
> +	if (__get_cpu_var(mce_fake_banks).valid) {
>  		int offset = msr_to_offset(msr);
> +		char *m = (char *)&__get_cpu_var(mce_fake_banks).injectm;
>  
>  		if (offset >= 0)
> -			*(u64 *)((char *)&__get_cpu_var(injectm) + offset) = v;
> +			*(u64 *)(m + offset) = v;
>  		return;
>  	}
>  	wrmsrl(msr, v);

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