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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] virtio-blk issues
Date: Tue, 3 Mar 2009 14:22:43 +0000
References: <20090303125411.GA16099@lst.de>
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To: qemu-devel@nongnu.org
Cc: Christoph Hellwig <hch@lst.de>

On Tuesday 03 March 2009, Christoph Hellwig wrote:
> I've been trying to move setup from kvm 72 in debian testing to the current
> qemu CVS.  The setup is using 7 virtio_blk disks and used to work on the
> old setup, but with current qemu the kernel (current Linus' HEAD from a few
> days ago) hangs when trying to setup the irq routing for the virtio_pci
> devices:
>
> virtio pci 0000:00:06.0: can't derive routing for PCI INT A
> virtio pci 0000:00:06.0: PCI INT A: no GSI - using IRQ 9

IIRC this is partly a bios issue. Real PIIX3 based systems never have more 
than ~5 PCI slots, so it doesn't have interrupt routing for more devices.

There are two solutions: Fix the bios to handle machines with large numbers of 
PCI slots, or have create multifunction PCI devices so lots of virtio 
instances don't use so many virtual PCI slots.

Paul