Re: [PATCH] 2.6.1-mm2: Get irq_vector size right for generic subarchUP installer kernels

[Mika Penttilä]

James Cleverdon wrote:

> On Wednesday 14 January 2004 8:36 pm, Zwane Mwaikambo wrote:
>  
>
> > On Wed, 14 Jan 2004, Nakajima, Jun wrote:
> >    
> >
> > > I tend to agree. I think the confusing part is the range of the IRQs on
> > > that machine. Assuming that irq_vector[NR_IRQ_VECTORS = 1024] requires
> > > more entries, then the IRQs should take that range, because
> > > IO_APCI_VECTOR(irq) is just irq_vector[irq], for example. If NR_IRQS is
> > > still 224, how can do_IRQ() can get the correct IRQ (i.e. >= 224) ? So
> > > in that case, the IRQ should be smaller than 224, then irq_vector[]
> > > should be smaller.
> > >      
> > In my opinion we should be breaking after we've exceeded the maximum
> > external vectors we can install. This will of course mean less than
> > the number of RTEs. James have you actually managed to use the devices
> > connected to the high (over ~224) RTEs?
> >    
>
> No, I haven't exceeded the available vectors, but wli has on a large NUMA-Q 
> box.
>
> The x440 and x445's problems are pre-reserving lots of bus numbers in the 
> BIOS, more than one per PCI slot.  They must be anticipating PCI cards with 
> bridge chips on them.
>
> I believe that the reason for irq_vector being so large is to allow IRQ (and 
> eventually vector) sharing.  The array is to map from RTE to vector.
>  
Any attempt to  setup an irq >= NR_IRQS will crash, because for instance 
entry.c interrupt stubs are an array of NR_IRQS entries...NR_IRQ_VECTORS 
> NR_IRQS really doesn't make sense as is.

We do support irq sharing among devices, but not vector sharing among 
irqs. For that the handler should loop through irq_vector[] to find 
every index, index != irq, irq_vector[index] == irq_vector[irq].

--Mika


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