[libvirt] [PATCH v2 10/25] qemu: capabilities: Add virtio/vhost {non-}transitional

[Cole Robinson]

On 1/29/19 11:05 AM, Andrea Bolognani wrote:
> On Tue, 2019-01-29 at 15:48 +0100, Ján Tomko wrote:
>> On Wed, Jan 23, 2019 at 04:32:38PM -0500, Cole Robinson wrote:
>>> This adds QEMU_CAPS flags for the following devices
>>>
>>>     virtio-blk-pci-transitional
>>>     virtio-blk-pci-non-transitional
>>>     virtio-net-pci-transitional
>>>     virtio-net-pci-non-transitional
>>>     vhost-scsi-pci-transitional
>>>     vhost-scsi-pci-non-transitional
>>>     virtio-rng-pci-transitional
>>>     virtio-rng-pci-non-transitional
>>>     virtio-9p-pci-transitional
>>>     virtio-9p-pci-non-transitional
>>>     virtio-balloon-pci-transitional
>>>     virtio-balloon-pci-non-transitional
>>>     vhost-vsock-pci-transitional
>>>     vhost-vsock-pci-non-transitional
>>>     virtio-input-host-pci-transitional
>>>     virtio-input-host-pci-non-transitional
>>>     virtio-scsi-pci-transitional
>>>     virtio-scsi-pci-non-transitional
>>>     virtio-serial-pci-transitional
>>>     virtio-serial-pci-non-transitional
>>
>> This seems excessive, is there a plan to retire the transitional
>> devices? I don't expect anyone creating a QEMU build that e.g.:
>> a) supports virtio-rng-pci-transitional but not virtio-rng-pci-non-transitional
>> b) supports virtio-scsi-pci-transitional but not virtio-input-host-pci-transitional
>>
>> For the disable-legacy property, we only have
>> QEMU_CAPS_VIRTIO_PCI_DISABLE_LEGACY, that is checked on multiple (but
>> not all possible) PCI devices.
> 
> That's a very good point! We could have a single capability
> 
>    QEMU_CAPS_VIRTIO_PCI_NON_TRANSITIONAL
> 
> that is set if any out of a bunch of {,non-}transitional devices
> is present, and key everything else off that...
> 
> Eduardo, do you think we might ever get in trouble if we did that?
> For example, because of QEMU dropping transitional devices but
> leaving non-transitional devices in?
> 

I believe eduardo is offline for the next few weeks, so I'll make this 
change in the next version to just track a single capability 
QEMU_CAPS_VIRTIO_PCI_NON_TRANSITIONAL

We can always add the fine grained capabilities later if needed.

Thanks,
Cole