[Xen-devel] Re: [PATCH 1/2] xen: events: do not workaround too-small nr_irqs

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Wed, 2011-02-09 at 16:21 +0000, Konrad Rzeszutek Wilk wrote: 
> On Wed, Feb 09, 2011 at 11:10:44AM +0000, Ian Campbell wrote:
> > This workaround was somewhat useful prior to the introduction of the
> > core irq allocator and 026c9d2d0d75 "xen: events: allocate GSIs and
> > dynamic IRQs from separate IRQ ranges." but should not be unnecessary now.
> > 
> > If nr_irqs turns out to be too small under Xen then we use (or define
> > if necessary) the interfaces to increase nr_irqs rather than working
> > around the core allocator in this way.
> > 
> > In my configuration NR_IRQS ends up being 2304 with nr_irq_gsi 272
> > which is sufficient.
> 
> Is this configuration where you run Xen + Linux under QEMU?

No, it was my physical test box.

If this change causes problems under qemu then we need to work with the
x86 guys to find a way to allow us to increase nr_irqs at start of day
when running under Xen (e.g. a generic interface to add headroom for
dynamic IRQs etc).

Ian.

> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> > ---
> >  drivers/xen/events.c |    7 -------
> >  1 files changed, 0 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > index 975e90f..ce33061 100644
> > --- a/drivers/xen/events.c
> > +++ b/drivers/xen/events.c
> > @@ -393,15 +393,8 @@ static int xen_allocate_irq_dynamic(void)
> >             first = get_nr_irqs_gsi();
> >  #endif
> >  
> > -retry:
> >     irq = irq_alloc_desc_from(first, -1);
> >  
> > -   if (irq == -ENOMEM && first > NR_IRQS_LEGACY) {
> > -           printk(KERN_ERR "Out of dynamic IRQ space and eating into GSI 
> > space. You should increase nr_irqs\n");
> > -           first = max(NR_IRQS_LEGACY, first - NR_IRQS_LEGACY);
> > -           goto retry;
> > -   }
> > -
> >     if (irq < 0)
> >             panic("No available IRQ to bind to: increase nr_irqs!\n");
> >  
> > -- 
> > 1.5.6.5



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