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? Thanks, -- Ming Lei
