[libvirt] [PATCH v5 02/16] qemu: Introduce qemuDomainDeviceDefValidateControllerAttributes

[John Ferlan]

On 01/29/2018 04:18 AM, Ján Tomko wrote:
> On Fri, Jan 05, 2018 at 06:47:25PM -0500, John Ferlan wrote:
>> Move the checks that various attributes are not set on any controller
>> other than SCSI controller using virtio-scsi model into the common
>> controller validate checks.
>>
>> Need to also add a qemuDomainResetSCSIControllerModel call in order
>> to ensure we get the "right" SCSI model if it's not set by default
>> since it wouldn't be set during post parse processing.
>>
> 
> So we should set it in post-parse processing once instead of adding this
> second call.
> 
> Jan

This is a point you raised in v3:

https://www.redhat.com/archives/libvir-list/2017-December/msg00293.html

to which I responded:

https://www.redhat.com/archives/libvir-list/2017-December/msg00304.html

and even carried into my v4:

https://www.redhat.com/archives/libvir-list/2018-January/msg00103.html

So, now that we're here again - the question becomes, do we really want
post parse processing to set a default model if it's not set? Should
that be part of this series? Should it be a followup? Should be
something done before this one and then rework this one?

Are there drawbacks to doing so?  One drawback that I kept coming back
to is that LSI becomes the default qemu model instead of VIRTIO-SCSI
(it's the order of setting *model in qemuDomainSetSCSIControllerModel).
That drawback caused problems when setting the model if we create a new
SCSI controller during something like hotplug because we had already
filled the current controller or when adding one VIRTIO-SCSI controller
but more than 7 disks (or hostdevs) that end up using that controller.
Although I think that's at least partially resolved by other changes
I've already made.

Tks -

John