On Tue, Sep 11, 2012 at 08:46:34AM -0500, Anthony Liguori wrote: > On 09/10/2012 01:24 AM, Michael S. Tsirkin wrote: > >On Mon, Sep 10, 2012 at 08:16:54AM +0200, Paolo Bonzini wrote: > >>Il 09/09/2012 00:40, Michael S. Tsirkin ha scritto: > >>>On Fri, Sep 07, 2012 at 06:00:50PM +0200, Paolo Bonzini wrote: > >>>>Il 07/09/2012 08:48, Nicholas A. Bellinger ha scritto: > >>>>>Cc: Stefan Hajnoczi<stefanha@xxxxxxxxxxxxxxxxxx> > >>>>>Cc: Zhi Yong Wu<wuzhy@xxxxxxxxxxxxxxxxxx> > >>>>>Cc: Michael S. Tsirkin<mst@xxxxxxxxxx> > >>>>>Cc: Paolo Bonzini<pbonzini@xxxxxxxxxx> > >>>>>Signed-off-by: Nicholas Bellinger<nab@xxxxxxxxxxxxxxx> > >>>>>--- > >>>>> hw/virtio-pci.c | 2 ++ > >>>>> hw/virtio-scsi.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ > >>>>> hw/virtio-scsi.h | 1 + > >>>>> 3 files changed, 52 insertions(+), 0 deletions(-) > >>>> > >>>>Please create a completely separate device vhost-scsi-pci instead (or > >>>>virtio-scsi-tcm-pci, or something like that). It is used completely > >>>>differently from virtio-scsi-pci, it does not make sense to conflate the > >>>>two. > >>> > >>>Ideally the name would say how it is different, not what backend it > >>>uses. Any good suggestions? > >> > >>I chose the backend name because, ideally, there would be no other > >>difference. QEMU _could_ implement all the goodies in vhost-scsi (such > >>as reservations or ALUA), it just doesn't do that yet. > >> > >>Paolo > > > >Then why do you say "It is used completely differently from > >virtio-scsi-pci"? Isn't it just a different backend? > > > >If yes then it should be a backend option, like it is > >for virtio-net. > > I don't mean to bike shed here so don't take this as a nack on > making it a backend option, but in retrospect, the way we did > vhost-net was a mistake even though I strongly advocated for it to > be a backend option. > > The code to do it is really, really ugly. I think it would have > made a lot more sense to just make it a device and then have it not > use a netdev backend or any other kind of backend split. > > For instance: > > qemu -device vhost-net-pci,tapfd=X We'd have to duplicate all tap options such as upscript then, and educate users that vhost-net-pci is in fact same as virtio-net-pci just faster. They have enough trouble guessing "-net-pci" in virtio-net-pci. IMHO a simple -device virtio-net-pci,vhost=on would have been the right thing to do in retrospect. > since vhost-net absolutely requires a tap fd, I think it's better in > the long run to not abuse the netdev backend to prevent user > confusion. In practice adding an option (even if it was in the wrong place) did not result in user confusion. Also in practice, renaming "virtio" to virtio-net-pci etc did create confusion. > Having a dedicated backend type that only has one > possible option and can only be used by one device is a bit silly > too. By now we can just enable it by default. This was always the idea. > So I would be in favor of dropping/squashing 3/5 and radically > simplifying how this was exposed to the user. Let's just make sure we don't have implementation tail wagging the user interface dog :) > > I would just take qemu_vhost_scsi_opts and make them device properties. > > Regards, > > Anthony Liguori > > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
