"Michael S. Tsirkin" <[email protected]> writes: > On Mon, Sep 22, 2025 at 03:26:23PM +0200, Christian Speich wrote: >> On Mon, Sep 22, 2025 at 09:08:47AM -0400, Michael S. Tsirkin wrote: >> > On Mon, Sep 22, 2025 at 01:49:55PM +0100, Daniel P. Berrangé wrote: >> > > On Mon, Sep 22, 2025 at 08:15:20AM -0400, Michael S. Tsirkin wrote: >> > > > On Mon, Sep 22, 2025 at 12:33:26PM +0100, Daniel P. Berrangé wrote: >> > > > > On Fri, Sep 19, 2025 at 04:07:19PM -0400, Michael S. Tsirkin wrote: >> > > > > > On Fri, Sep 19, 2025 at 04:30:53PM +0200, Christian Speich wrote: >> > > > > > > This removes the change introduced in [1] that prevents the use >> > > > > > > of >> > > > > > > vhost-user-device and vhost-user-device-pci on unpatched QEMU >> > > > > > > builds. >> > > > > > > >> > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 >> > > > > > > >> > > > > > > Signed-off-by: Christian Speich <[email protected]> >> > > > > > > --- >> > > > > > > vhost-user-device and vhost-user-device-pci started out as user >> > > > > > > creatable devices. This was changed in [1] when the >> > > > > > > vhost-user-base was >> > > > > > > introduced. >> > > > > > > >> > > > > > > The reason given is to prevent user confusion. Searching >> > > > > > > qemu-discuss or >> > > > > > > google for "vhost-user-device" I've seen no confused users. >> > > > > > > >> > > > > > > Our use case is to provide wifi emulation using >> > > > > > > "vhost-user-device-pci", >> > > > > > > which currently is working fine with the QEMU 9.0.2 present in >> > > > > > > Ubuntu >> > > > > > > 24.04. With newer QEMU versions we now need to patch, distribute >> > > > > > > and >> > > > > > > maintain our own QEMU packages, which is non-trivial. >> > > > > > > >> > > > > > > So I want to propose lifting this restriction to make this >> > > > > > > feature >> > > > > > > usable without a custom QEMU. >> > > > > > > >> > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 >> > > > > > >> > > > > > The confusion is after someone reuses the ID you are claiming >> > > > > > without >> > > > > > telling anyone and then linux guests will start binding that >> > > > > > driver to >> > > > > > your device. >> > > > > > >> > > > > > >> > > > > > We want people doing this kind of thing to *at a minimum* >> > > > > > go ahead and register a device id with the virtio TC, >> > > > > > but really to write and publish a spec. >> > > > > >> > > > > Wanting people to register a device ID is a social problem and >> > > > > we're trying to apply a technical hammer to it, which is rarely >> > > > > an productive approach. >> > > > > >> > > > > If we want to demonstrate that vhost-user-device is "risky", then >> > > > > how about we rename it to have an 'x-' prefix and thus disclaim >> > > > > any support for it, but none the less allow its use. Document it >> > > > > as an experimental device, and if it breaks, users get to keep >> > > > > both pieces. >> > > > >> > > > Maybe with the insecure tag you are working on? >> > > >> > > Sure. >> > > >> > > > And disable in the default config? >> > > >> > > Disabling in default config would retain the very problem that Christian >> > > is trying to solve - that no distro would have the functionality >> > > available >> > > for users. >> > >> > I think his problem is that he has to patch qemu. >> >> Yes I'm trying to avoid that. Patching qemu also involes providing updates >> (and security patches!) for it. This is a very high burden to turn this >> simple flag on. >> >> > >> > As described, this is a developer option not an end user one. >> >> I don't really get the distintion between developer and end user here. >> >> As a developer I'm an end user too, I'm concerned with the linux kernel >> and the additional host tooling for mac80211_hwsim support but QEMU >> I'm just using as an user. >> >> Greetings, >> Christian > > Are you ok with building qemu with an extra config flag?
In my patch I gated the feature on: VHOST_USER_TEST so it's easy to patch out of the default config. > > > >> > >> > >> > I know Red Hat will disable it anyway - we support what we ship. >> > >> > >> > > With regards, >> > > Daniel >> > > -- >> > > |: https://berrange.com -o- >> > > https://www.flickr.com/photos/dberrange :| >> > > |: https://libvirt.org -o- >> > > https://fstop138.berrange.com :| >> > > |: https://entangle-photo.org -o- >> > > https://www.instagram.com/dberrange :| >> > >> > -- Alex Bennée Virtualisation Tech Lead @ Linaro
