[virt-tools-list] scsi controller issue in 'customize before install'

Cole Robinson crobinso at redhat.com
Wed Oct 18 23:28:07 UTC 2017

On 10/12/2017 04:58 AM, Lin Ma wrote:
> Hi list,
> I have a question about scsi controller while I create vm.
> For a existed vm, When user changed a virtual disk's bus type to scsi In
> VM details page,
> Then click 'apply' button, If this vm's configuration doesn't have any
> scsi controller, Libvirt
> will automatically add one and trigger a lifecycle event. Virt-manager
> rely on the event to
> refresh vm's hardware list, Then user can see the scsi controller which
> is automatically
> added by libvirt.
> But when user installs a vm through virt-manager GUI, In VM details
> page(customize before
> install), User changes a virtual disk's bus type to scsi, Then click
> 'apply' button, There is no
> scsi controller in hardware list because libvirt won't help user to add
> a default scsi controller
> until user clicks 'Begin Installation' button. user may get user confused.
> In this case, If user wants to use virtio-scsi instead of the default
> one, User needs to manually
> add a scsi controller then change the scsi controller model.
> I refered to the logic of 'adding disk', want to write a patch to modify
> the logic of 'changing
> disk bus' to: Add a virtio-scsi scsi controller if needed while user
> change disk bus to scsi
> instead of relying on libvirt lifecycle event, Then user can see the
> scsi controller in hardware
> list before install.
> I'm not sure if the idea makes sense, or perhaps this is not an issue.
> So may I have your idea?

I think adding a convenience option for specifically for virtio-scsi
would be helpful, like bus=virtio-scsi instead of just bus=scsi. That
has confused people off and on for a while.

I think there's also a reasonable case to be made to add a virtio-scsi
controller to new VMs by default anyways, if the OS supports it, even if
we don't use it for disks by default. But that's a separate discussion


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