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

[Cornelia Huck]

On Tue, 17 Jun 2014 14:06:25 +0200
Alexander Graf <address@hidden> wrote:

> 
> On 17.06.14 14:04, Cornelia Huck wrote:
> > On Tue, 17 Jun 2014 18:45:09 +0800
> > Ming Lei <address@hidden> wrote:
> >
> >> On Tue, Jun 17, 2014 at 6:40 PM, Ming Lei <address@hidden> wrote:
> >>> On Tue, Jun 17, 2014 at 6:25 PM, Cornelia Huck <address@hidden> wrote:
> >>>> On Tue, 17 Jun 2014 18:15:39 +0800
> >>>> Ming Lei <address@hidden> wrote:
> >>>>
> >>>>> On Tue, Jun 17, 2014 at 4:46 PM, Cornelia Huck <address@hidden> 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.