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 14:04, 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?


Alex