[Engine-devel] Issues with VirtIO-SCSI

[Vitor de Lima]

Hi Daniel,

I asked this question because I have implemented a filter to show only compatible disk interfaces (in change #17964). The main purpose of this patch is to hide the IDE interface type when creating disks for PPC64 VMs (since IDE is not supported on this architecture). If it was decided that the VirtIO-SCSI interface type should be hidden from the user in case it was disabled, I would have to modify that patch a little bit.

Another issue is that in change #18622 the support for a PPC64-specific controller, the SPAPR VSCSI controller, was introduced. But the code was created based on the assumption that the VirtIO-SCSI controller was always present, and this isn't the case anymore. And another patch that I will work on really soon will add support to create disks that are connected to this interface.

So, I would like some feedback before changing these patches. Is a validation on the backend enough to block the user from using an inexistent controller? Should the frontend be changed as well? What would be a good approach to handle multiple SCSI controllers in a VM (were the presence of one of them is optional)?

Thanks,
Vitor



>-----Original Message-----
>From: Daniel Erez [mailto:derez at redhat.com]
>Sent: segunda-feira, 23 de setembro de 2013 17:06
>To: Vitor de Lima
>Cc: engine-devel at ovirt.org
>Subject: Re: [Engine-devel] Issues with VirtIO-SCSI
>
>Hi Vitor,
>
>The new VirtIO-SCSI enabled checkbox is an indication whether to attach a
>VirtIO-SCSI controller when running the VM.
>It should be enabled automatically on cluster >= 3.3.
>
>When disabled, I think it's preferable not to add a new controller automatically
>when running the VM as it requires creating/attaching a new VmDevice -
>which we refrain of on VmInfoBuilder flows (and since it might be confusing to
>the user...).
>
>As an alternative, I've planned to add a warning in the dialog or create a canDo
>message to prevent running the VM at all.
>I'm not sure we should hide the option from disk interfaces list as it's already
>being filtered using VirtIoScsiEnabled ConfigurationValue (and using OsInfo
>soon...).
>
>Let me know what you think and thanks a lot for the input!
>
>Daniel
>
>----- Original Message -----
>> From: "Vitor de Lima" <vitor.lima at eldorado.org.br>
>> To: engine-devel at ovirt.org
>> Sent: Monday, September 23, 2013 10:42:39 PM
>> Subject: [Engine-devel] Issues with VirtIO-SCSI
>>
>> Hi everyone,
>>
>> I have found some issues with this patch:
>>
>> http://gerrit.ovirt.org/#/c/18638/
>>
>> It allows the user to disable the VirtIO-SCSI disk interface during
>> the VM creation. The problem is that the user still can add, attach
>> and hotplug disks with the VirtIO-SCSI interface type, but when the
>> user does so, libvirt automatically creates a LSI Logic SCSI
>> controller and connects the new disk to it.
>>
>> How can this problem be solved? Should the VirtIO-SCSI interface type
>> be hidden from the user in case it wasn't enabled, or should the
>> engine enable the VirtIO-SCSI controller, hotplug it, then hotplug the
>> disk into it transparently?
>>
>> Thanks,
>> Vitor de Lima
>>
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