On Wed, 2014-07-02 at 18:48 -0600, Eric Blake wrote:
On 07/02/2014 06:28 PM, Nicholas A. Bellinger wrote:
QEMU is not the only hypervisor that libvirt targets, so tieing libvirt names to QEMU names is a non-goal. We pick the names that make most sense in the context of libvirt.
Not sure I follow.. virtio-scsi is specific to QEMU/KVM, and per the comment in the original patch:
'Currently it only supports attribute <code>queues</code> (<span class="since">1.0.5</span>, QEMU and KVM only)'
would seem to indicate the parameter names are only used in the context of QEMU/KVM, no..?
Just because qemu is the only hypervisor driver that _currently_ uses the feature doesn't preclude the libxl hypervisor from _also_ gaining support for the feature in a future libvirt release, at which point the documentation would mention the new version number for the additional use of the feature. Again, the name qemu chose is not necessarily the best name compared to what it might map to in libxl or any other hypervisor, so libvirt tries to pick names that are consistent with other libvirt terms, even if they don't match underlying qemu names.
It's worth mentioning that these names are coming directly from the Linux SCSI subsystem tunables that are read from virtio-scsi config space and set during drivers/scsi/virtio_scsi.c:virtscsi_probe() init time, and did *not* originate with QEMU.
If the virtio-scsi parameters are intended to be used across hypervisors, then matching them to QEMU's own names doesn't really matter. But if they are specific to virtio-scsi and only used by QEMU/KVM instances, then renaming them to something arbitrary to libvirt is pointless and confusing.
virtio is not necessarily a qemu-only concept.
The point is that if a potential port of virtio-scsi to Xen ever happens, it will use the same parameter names that every Linux SCSI LLD has been using for the last 20 years. Eg: They will be the same parameters names that the virtio-scsi LLD pulls out of configuration space, regardless of if it's KVM or XEN. --nab