On Tue, 17 Jun 2014 18:45:09 +0800 Ming Lei <ming....@canonical.com> wrote:
> On Tue, Jun 17, 2014 at 6:40 PM, Ming Lei <ming....@canonical.com> wrote: > > On Tue, Jun 17, 2014 at 6:25 PM, Cornelia Huck <cornelia.h...@de.ibm.com> > > wrote: > >> On Tue, 17 Jun 2014 18:15:39 +0800 > >> Ming Lei <ming....@canonical.com> wrote: > >> > >>> On Tue, Jun 17, 2014 at 4:46 PM, Cornelia Huck <cornelia.h...@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?
