From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 4/5] virtio-scsi: Add start/stop functionality for vhost-scsi Date: Tue, 11 Sep 2012 08:46:34 -0500 Message-ID: <504F40BA.7020800__28822.6401935846$1347371246$gmane$org@us.ibm.com> References: <1347000499-28701-1-git-send-email-nab@linux-iscsi.org> <1347000499-28701-5-git-send-email-nab@linux-iscsi.org> <504A1A32.5050705@redhat.com> <20120908224032.GC20588@redhat.com> <504D85D6.2090703@redhat.com> <20120910062437.GD16819@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120910062437.GD16819@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: Stefan Hajnoczi , kvm-devel , Jan Kiszka , qemu-devel , lf-virt , Anthony Liguori , target-devel , Paolo Bonzini , Zhi Yong Wu , Christoph Hellwig List-Id: virtualization@lists.linuxfoundation.org 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 >>>>> Cc: Zhi Yong Wu >>>>> Cc: Michael S. Tsirkin >>>>> Cc: Paolo Bonzini >>>>> Signed-off-by: Nicholas Bellinger >>>>> --- >>>>> 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 I know this breaks the model of separate backends and frontends but 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. Having a dedicated backend type that only has one possible option and can only be used by one device is a bit silly too. So I would be in favor of dropping/squashing 3/5 and radically simplifying how this was exposed to the user. I would just take qemu_vhost_scsi_opts and make them device properties. Regards, Anthony Liguori >