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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Feb 16, 2011 at 04:14:17PM +0000, Ian Campbell wrote:
> On Tue, 2011-02-15 at 15:15 +0000, Ian Campbell wrote:
> > 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?
> > 
> > I've just tried these two patches under qemu, booting a 64 bit
> > xen-unstable hypervisor with a 32 bit domain 0 kernel, pxeboot using:
> >         qemu-system-x86_64 -m 256 -vnc 0.0.0.0:1 -k en-gb -serial stdio 
> > -boot nc \
> >             -usb -usbdevice tablet -net 
> > nic,vlan=0,macaddr=00:16:3e:f7:c4:1d,model=e1000 \
> >             -net tap,vlan=0,ifname=tapQEMU.0 -hda /dev/VG/debian-HVM-1 
> >         
> > There I appear to get:
> >         nr_irqs_gsi: 272
> >         NR_IRQS:2304 nr_irqs:256 16
> > 
> > which leads to a failure due to not being able to allocate a dynamic IRQ
> > (because 272 > 256!), I'll dig into this...
> 
> The solution is to increase nr_irqs, which is currently static after
> boot even with sparseirqs.
> 
> Fortunately tglx intends to make this dynamically growable in the IRQ
> core in the 2.6.39 time frame which nicely ties in with this patch.

OK. Can you point me to tglx's git tree that brings these goodies in?

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