Re: [Qemu-devel] [QEMU question] Disk hot plugging without working PCI hotplug - possible?

[Frederic Konrad <fred.konrad@greensocs.com>]

On 06/06/2013 12:13, Alexey Kardashevskiy wrote:
> Hi!
>
> For the pseries platform (server PPC64) we do not support PCI hotplug yet.
> However we still want to hot plug disks.
>
> As a workaround, we could add multiple SCSI host devices (virtio-scsi-pci,
> spapr-vscsi) without any disk attached and later (using qemu console)
> attach drives to them as we do with the "-drive" parameter in the command line.
>
> So I enabled CONFIG_PCI_HOTPLUG_OLD=y and tried.
>
> However, drive_add console command works only with PCI what eliminates
> "spapr-vscsi" from the list. Oookay.
>
> Then I tried running qemu with "-device virtio-scsi-pci,id=device0" and
> later doing "drive_add 0 file=virtimg/test1" from the qemu console. This
> time qemu responded with "Device is not a SCSI adapter" what is correct as
> nowadays virtio-XXXX-pci devices are not what are they called as they
> simply create underlying virtio-bus, attach a real virtio-XXXX-device there
> (which is not PCI) and only then attach disk to non-PCI virtio device.
Hi,

Seems it's a bug: il should be compatible with the old virtio-scsi-pci.
What's the meaning of the "0" in drive_add command?

Fred
>
> So as I see there is no way to attach a disk to an existing controller in
> already running qemu.
>
> This is how I add disks to qemu now:
>   -device virtio-scsi-pci,id=virtioscsi0 \
>   -drive file=virtimg/fc18guest,if=none,id=drive0,readonly=off,
> format=raw,media=disk,werror=stop,rerror=stop \
>   -device scsi-disk,id=scsidisk0,bus=virtioscsi0.0,channel=0,
> scsi-id=0,lun=0,drive=drive0,removable=off \
>
> I want to only add "-device virtio-scsi-pci,id=virtioscsi0" to the command
> line and do the rest from the qemu console.
>
> Am I missing some useful command from qemu console or anything else? Thanks!
>
>