Re: [Qemu-devel] virtio-blk issues

[Avi Kivity <avi@redhat.com>]

Paul Brook wrote:
> 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.
>
>   

The kvm bios supports 32 slots; I don't know if upstream bochs picked up 
these changes.

In any case I'd like to see a virtio-blk controller which can support an 
arbitrary number of disks, much like a SCSI controller.  A pci slot or 
function per disk is wasteful.

-- 
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