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

[Alexey Kardashevskiy]

On 06.06.2013 22:44, Frederic Konrad wrote:
> 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?

It is a PCI slot number, the complete address would include a domain and
a bus.


> 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!


-- 
With best regards

Alexey Kardashevskiy -- icq: 52150396