Re: [Qemu-devel] [PATCH 2/4] s390-virtio-bus: move common virtio properties to virtio s390 device class

[Alexander Graf <agraf@suse.de>]

On 17.06.14 14:56, Cornelia Huck wrote:
> On Tue, 17 Jun 2014 14:06:25 +0200
> Alexander Graf <agraf@suse.de> wrote:
>
>> On 17.06.14 14:04, Cornelia Huck wrote:
>>> On Tue, 17 Jun 2014 18:45:09 +0800
>>> Ming Lei <ming.lei@canonical.com> wrote:
>>>
>>>> On Tue, Jun 17, 2014 at 6:40 PM, Ming Lei <ming.lei@canonical.com> wrote:
>>>>> On Tue, Jun 17, 2014 at 6:25 PM, Cornelia Huck <cornelia.huck@de.ibm.com> wrote:
>>>>>> On Tue, 17 Jun 2014 18:15:39 +0800
>>>>>> Ming Lei <ming.lei@canonical.com> wrote:
>>>>>>
>>>>>>> On Tue, Jun 17, 2014 at 4:46 PM, Cornelia Huck <cornelia.huck@de.ibm.com> wrote:
>>>>>>>>> Looks like s390 virtio-blk never enables the two common features, is
>>>>>>>>> there any reason the two features can't be supported by s390?
>>>>>>>> Indirect descriptors are fine. event_idx will not work IIUC because we
>>>>>>>> always need to do a sync before we see changes, and this needs an
>>>>>>>> interrupt to trigger.
>>>>>>> Sounds like the old s390 isn't cache coherent? Because you mean
>>>>>>> write in one side can only be observed from another side with an
>>>>>>> explicit notification or interrupt.
>>>>>>>
>>>>>>> On arm/arm64, we didn't see any problem with event_idx.
>>>>>> But you probably have the queues in guest memory, as on other
>>>>>> transports (including virtio-ccw)? The old s390-virtio transport keeps
>>>>>> the devices and their virtqueues in a memory area behind the guest
>>>>>> memory - the guest does not see that memory directly, but a sync has to
>>>>>> be performed to see virtqueue movement (see s390_virtio_device_sync()).
>>>>> OK, it looks like a real physical device, :-)
>>>>>
>>>>> I will keep s390-virtio as it is, thanks for your explanation.
>>>> BTW, do you want me to add DEFINE_VIRTIO_COMMON_FEATURES()
>>>> to s390_virtio_net_properties and s390_virtio_scsi_properties since
>>>> I remove them from their default properties?
>>> It might be better to remove them for good :)
>>>
>>> Nobody has probably tried to use them for some time...
>>> I just start a very minimal guest with a virtio-console and a
>>> virtio-blk device. Don't know whether Alex has a more advanced setup
>>> at hand?
>> It's the only target that works with TCG, no?
> Yup. Do you have a test setup with net, scsi, ...? I usually test
> networking (for example) only via a libvirt setup, which will only work
> with virtio-ccw.

I don't regularly test it, but OBS uses that target for example.


Alex