Re: [Xen-devel] [RFC][PATCH] xen/apic: refactor error_interrupt

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.05.15 at 04:03, <tiejun.chen@xxxxxxxxx> wrote:
> --- a/xen/arch/x86/apic.c
> +++ b/xen/arch/x86/apic.c
> @@ -1319,28 +1319,37 @@ out: ;
>   * This interrupt should never happen with our APIC/SMP architecture
>   */
>  
> +static const char *apic_fault_reasons[] =

If at all, then this should be const. But...

> +{
> +    "Send CS error",
> +    "Receive CS error",
> +    "Send accept error",
> +    "Receive accept error",
> +    "Reserved",
> +    "Send illegal vector",
> +    "Received illegal vector",
> +    "Illegal register address",
> +};
> +
> +static const char *apic_get_fault_reason(u8 fault_reason)
> +{
> +    return apic_fault_reasons[fault_reason];
> +}
> +
>  void error_interrupt(struct cpu_user_regs *regs)
>  {
>      unsigned long v, v1;
> +    const char *reason;
>  
>      /* First tickle the hardware, only then report what went on. -- REW */
>      v = apic_read(APIC_ESR);
>      apic_write(APIC_ESR, 0);
>      v1 = apic_read(APIC_ESR);
>      ack_APIC_irq();
> +    reason = apic_get_fault_reason(ffs(v1) - 1);

... I'm not convinced - you're treating errors represented by lower
bits "better" than higher ones. And if there are multiple errors, then
spelling out one but not the other may end up being confusing.
These errors should be rare enough to warrant manually looking up
the individual bits' meanings.

Jan

> -    /* Here is what the APIC error bits mean:
> -       0: Send CS error
> -       1: Receive CS error
> -       2: Send accept error
> -       3: Receive accept error
> -       4: Reserved
> -       5: Send illegal vector
> -       6: Received illegal vector
> -       7: Illegal register address
> -    */
> -    printk (KERN_DEBUG "APIC error on CPU%d: %02lx(%02lx)\n",
> -            smp_processor_id(), v , v1);
> +    printk (KERN_DEBUG "APIC error on CPU%d: %02lx(%02lx):%s.\n",
> +            smp_processor_id(), v , v1, reason);
>  }
>  
>  /*



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