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.