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[80.230.85.71]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4606c0c2059sm1493714f8f.6.2026.06.11.13.45.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 13:45:14 -0700 (PDT) Date: Thu, 11 Jun 2026 16:45:10 -0400 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Cc: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Peter Maydell , Stefan Hajnoczi , Dorinda Bassey , Albert Esteve , Alex =?iso-8859-1?Q?Benn=E9e?= , qemu-devel , virtio-comment@lists.linux.dev, dev@lists.cloudhypervisor.org, rust-vmm@lists.opendev.org, Stefano Garzarella , Manos Pitsidianakis , Demi Marie Obenour , Alyssa Ross , Mark Burton , Matti Moell , Viresh Kumar , Sergio Lopez , Vishwanath Seshagiri , Rob Bradford , Zhengyu Zhao , "Jorge E. Moreira" Subject: Re: Where should the vhost-user specification live? Message-ID: <20260611164404-mutt-send-email-mst@kernel.org> References: <20260601151815.GC411459@fedora> <20260601160352-mutt-send-email-mst@kernel.org> <20260604162853.GC115597@fedora> <20260611203915.GB237427@fedora> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260611203915.GB237427@fedora> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jun 11, 2026 at 04:39:15PM -0400, Stefan Hajnoczi wrote: > On Wed, Jun 10, 2026 at 09:37:10AM +0100, Daniel P. Berrangé wrote: > > On Tue, Jun 09, 2026 at 08:51:15PM +0100, Peter Maydell wrote: > > > On Tue, 9 Jun 2026 at 20:45, Stefan Hajnoczi wrote: > > > > > > > > On Tue, Jun 9, 2026 at 2:51 PM Peter Maydell wrote: > > > > > > > > > > On Tue, 9 Jun 2026 at 19:00, Stefan Hajnoczi wrote: > > > > > > I'm not sure if anyone brought up this topic on qemu-devel and with > > > > > > Michael before. As I mentioned in my reply, there are ways to avoid > > > > > > blocking vhost-user spec changes when qemu.git is frozen: > > > > > > > > > > > > The simplest approach is to keep merging vhost-user.rst changes during > > > > > > freeze since it does not jeopardize the release or introduce > > > > > > instability. > > > > snip > > > > > I tend to view the specs subsection of the docs as being > > > for things where either QEMU really is the authoritative > > > source (eg fw_cfg), or where the spec is for something that's > > > basically moribund and has no better home. If vhost-user is > > > a cross-project specification that it so active that it > > > cannot live within QEMU's release process, then I think > > > it deserves to have its own independent home. > > > > Yes, the main impression I get having read through this whole thread > > is that vhost-user spec should have its own home outside QEMU. > > > > We can come up with all sorts of rationalizations for how to make > > things work in the context of QEMU, but they all just come across > > as excuses to avoid changing the fairly arbitrary historical use > > of qemu.git. Even if as QEMU maintainers we consider that we're a > > "neutral" home, I can understand why it might not be perceived that > > way from the outside. > > > > If people want agility such that we need to make exceptions for > > our rules during freeze that is one flag that it doesn't belong > > with the main qemu.git, but there are broader points that are > > pushing my view in that direction too. > > > > > > Not mentioned is that engaging with the QEMU mailing list as a > > non-regular QEMU contributor is not a very attractive task. > > While QEMU may be satisfied with email, QEMU are in a tiny > > minority these days. The rest of the OSS community has > > decided that git forges are the better way to collaborate. > > > > Our dev list is very high volume, with changes very easily (and > > often) lost in the noise, even from regular contributors, such > > that we have to teach people to (repeatedly) "ping" to attract > > attention. > > A separate repo in a git forge definitely has the advantage of making > communication easier to follow for anyone interested only in the > vhost-user protocol. > > > If we want agility though, IMHO it is best to stay away from the > > bureucracy of the OASIS virtio spec / committee, which is a big > > turn off IME. > > Yes, OASIS adds overhead. > > The downside is that vhost-user suffers from being outside the VIRTIO > spec umbrella. It's really a VIRTIO Transport and would benefit from the > discipline of actually being part of the spec as such. At the moment > vhost-user is not really bound to VIRTIO through any interface (i.e. > VIRTIO Transport) or device lifecycle that is guaranteed to align with > the VIRTIO spec. This has led to both design problems and bugs that > would be prevented by making it a VIRTIO Transport. > > In addition to the OASIS overhead you mentioned, the other issue is that > moving vhost-user into the VIRTIO spec would require reconciling the > the vhost-user protocol with the VIRITO Transport's interface and also > rewriting parts of the vhost-user spec that are not up to the level > (e.g. adding conformance clauses, eliminating some informal language, > etc). And possibly getting an agreement to OASIS IPR from major past contributors. > In other words, it's a bunch of work. Although from a purist perspective > I think it's the right place for vhost-user, I think it would be an > unpopular solution. > > > If we're considering a move of the spec, we should probably consider > > the best home for some of the related code parts too: > > > > subprojects/libvhost-user/ > > contrib/vhost-user-blk/ > > contrib/vhost-user-bridge/ > > contrib/vhost-user-gpu/ > > contrib/vhost-user-input/ > > contrib/vhost-user-scsi/ > > > > IIUC, the subprojects is fully standalone code with no dependency > > on QEMU. It remained within QEMU for "convenience" allowing us to > > consume them from the impls under contrib/. While the contrib code > > has some depedencies on QEMU, overall they appear pretty light and > > so likely easily detached > > > > $ git grep '#include "' vhost-user-* | awk '{print $2}' | sort | uniq > > "hw/virtio/virtio-gpu-bswap.h" > > "hw/virtio/virtio-gpu-pixman.h" > > "libvhost-user-glib.h" > > "libvhost-user.h" > > "qapi/error.h" > > "qemu/atomic.h" > > "qemu/bswap.h" > > "qemu/ctype.h" > > "qemu/drm.h" > > "qemu/iov.h" > > "qemu/osdep.h" > > "qemu/queue.h" > > "qemu/sockets.h" > > "standard-headers/linux/input.h" > > "standard-headers/linux/virtio_blk.h" > > "standard-headers/linux/virtio_gpu.h" > > "standard-headers/linux/virtio_input.h" > > "standard-headers/linux/virtio_net.h" > > "standard-headers/linux/virtio_scsi.h" > > "virgl.h" > > "vugbm.h" > > "vugpu.h" > > > > > > We have a often repeated desire to eliminate the "contrib" tree > > as a concept, since it is currently effectively a "dumping ground" > > for things which are either unmaintained or didn't have a better > > home yet. This might be a chance to provide a better home for a > > big part of it. > > > > IMHO this suggests it is worth creating a new top level gitlab project > > for it all to live in and form a dedicated team around it, rather than > > trying to pick any existing location. > > Some vhost-user back-ends in the contrib/ directory are used by QEMU's > test suite. An alternative way of integrating them into the tests could > be found, but I wanted to mention that dependency. > > Stefan