[libvirt] Support for more than 32 virtio devices

[Daniel P. Berrange]

On Tue, May 03, 2011 at 05:31:02PM -0500, Anthony Liguori wrote:
> On 05/03/2011 09:33 AM, Daniel P. Berrange wrote:
> >On Mon, May 02, 2011 at 08:09:07AM -0700, Badari Pulavarty wrote:
> >>Hi,
> >>
> >>How can I make use of "multifunction" functionality to support
> >>more than 32 virtio devices in QEMU through libvirt ?
> >
> >It isn't supported because it doesn't work with hotplug.
> 
> And to be clear, on the QEMU side, we really need to have a high
> level modelling of a multifunction device.  So the following should
> be possible:
> 
> -device virtio-blk-pci,ports=4,drive0=hda,drive1=hdb,drive2=hdc,...
> 
> Then libvirt could add/remove all ports in a single operation.

Having to add/remove all ports at once is still an undesirable
restriction on mgmt applications, hence the desire for a proper
virtio block controller which allows multiple drives in the
same way as LSI SCSI does today. Once we have the latter I don't
really see much point in using multifunction virtio block.

> >>Are there corresponding changes in libvirt ?
> >
> >To increase the number of devices in a usable manner, we we're waiting
> >for QEMU to support either
> >
> >  - A virtio block controller with multiple disks
> >  - A PCI bridge to allow>  28 PCI devices


Daniel
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