Re: [Xen-devel] [PATCH 8/9] x86/IRQ: make fixup_irqs() skip unconnected internally used interrupts

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.05.19 at 15:52, <roger.pau@xxxxxxxxxx> wrote:
> On Mon, Apr 29, 2019 at 05:26:41AM -0600, Jan Beulich wrote:
>> --- a/xen/arch/x86/irq.c
>> +++ b/xen/arch/x86/irq.c
>> @@ -2412,8 +2412,20 @@ void fixup_irqs(const cpumask_t *mask, b
>>          vector = irq_to_vector(irq);
>>          if ( vector >= FIRST_HIPRIORITY_VECTOR &&
>>               vector <= LAST_HIPRIORITY_VECTOR )
>> +        {
>>              cpumask_and(desc->arch.cpu_mask, desc->arch.cpu_mask, mask);
>>  
>> +            /*
>> +             * This can in particular happen when parking secondary threads
>> +             * during boot and when the serial console wants to use a PCI 
>> IRQ.
>> +             */
>> +            if ( desc->handler == &no_irq_type )
> 
> I found it weird that a irq has a vector assigned (in this case a
> high-priority vector) but no irq type set.
> 
> Shouldn't the vector be assigned when the type is set?

In general I would agree, but the way the serial console IRQ
gets set up is different - see smp_intr_init(). When it's a PCI
IRQ (IO-APIC pin 16 or above), we'll know how to program
the IO-APIC RTE (edge/level, activity high/low) only when
Dom0 boots, and hence we don't set ->handler early.

Jan



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