Re: [Xen-devel] [PATCH v2 3/6] x86: track when in #MC context

[Julien Grall <julien@xxxxxxx>]

Hi Roger,

On 17/02/2020 18:43, Roger Pau Monne wrote:
> Add helpers to track when executing in #MC context. This is modeled
> after the in_irq helpers.
>
> Note that there are no users of in_mc() introduced by the change,
> further users will be added by followup changes.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>   xen/arch/x86/cpu/mcheck/mce.c | 2 ++
>   xen/include/asm-x86/hardirq.h | 5 +++++
>   xen/include/xen/irq_cpustat.h | 1 +
>   3 files changed, 8 insertions(+)
>
> diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
> index d61e582af3..93ed5752ac 100644
> --- a/xen/arch/x86/cpu/mcheck/mce.c
> +++ b/xen/arch/x86/cpu/mcheck/mce.c
> @@ -93,7 +93,9 @@ void x86_mce_vector_register(x86_mce_vector_t hdlr)
>   
>   void do_machine_check(const struct cpu_user_regs *regs)
>   {
> +    mc_enter();
>       _machine_check_vector(regs);
> +    mc_exit();
>   }
>   
>   /*
> diff --git a/xen/include/asm-x86/hardirq.h b/xen/include/asm-x86/hardirq.h
> index 34e1b49260..af3eab6a4d 100644
> --- a/xen/include/asm-x86/hardirq.h
> +++ b/xen/include/asm-x86/hardirq.h
> @@ -8,6 +8,7 @@ typedef struct {
>         unsigned int __softirq_pending;
>         unsigned int __local_irq_count;
>         unsigned int __nmi_count;
> +       unsigned int mc_count;
>         bool_t __mwait_wakeup;
>   } __cacheline_aligned irq_cpustat_t;
>   
> @@ -18,6 +19,10 @@ typedef struct {
>   #define irq_enter()   (local_irq_count(smp_processor_id())++)
>   #define irq_exit()    (local_irq_count(smp_processor_id())--)
>   
> +#define in_mc() 	(mc_count(smp_processor_id()) != 0)
> +#define mc_enter()     (mc_count(smp_processor_id())++)
> +#define mc_exit()      (mc_count(smp_processor_id())--)
> +
>   void ack_bad_irq(unsigned int irq);
>   
>   extern void apic_intr_init(void);
> diff --git a/xen/include/xen/irq_cpustat.h b/xen/include/xen/irq_cpustat.h
> index 73629f6ec8..12b932fc39 100644
> --- a/xen/include/xen/irq_cpustat.h
> +++ b/xen/include/xen/irq_cpustat.h
> @@ -26,5 +26,6 @@ extern irq_cpustat_t irq_stat[];
>   #define local_irq_count(cpu)  __IRQ_STAT((cpu), __local_irq_count)
>   #define nmi_count(cpu)                __IRQ_STAT((cpu), __nmi_count)
>   #define mwait_wakeup(cpu)     __IRQ_STAT((cpu), __mwait_wakeup)
> +#define mc_count(cpu)          __IRQ_STAT((cpu), mc_count)
The header is only meant to contain arch-independent IRQ stats (see 
comment a few lines above). This is unlikely to be used on Arm, so can 
you move this into an x86 specific header?
Cheers,

--
Julien Grall

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