Date: Tue, 28 Jul 2026 13:59:34 +0200 From: vermaden <vermaden@interia.pl> To: yi zishun <zishun.yi.dev@gmail.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Cc: "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org> Subject: Re: Worth adding another graphics option to bhyve? Message-ID: <gyqbhbwlecjsmxnfowgl@fsrj> In-Reply-To: <CABjVtiZc-y9H0ob8Fxk94zpsSpsp5qZcPSSg0q4geLq3S0S7rw@mail.gmail.com>
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Temat: Worth adding another graphics option to bhyve? Data: 2026-07-28 13:48 Nadawca: "yi zishun" <zishun.yi.dev@gmail.com> Adresat: "FreeBSD Hackers" <freebsd-hackers@freebsd.org>; DW: freebsd-virtualization@freebsd.org; > Hi, hackers > > As the title suggests, briefly speaking, the proposed option > is a combination of "vhost-user-gpu" and another display > backend (for example, a D-Bus backend). > > Currently, bhyve has two main approaches for graphics > rendering and display. One is fbuf+VNC for 2D graphics, > and the other is GPU passthrough mainly for 3D workloads. > Both approaches have some obvious drawbacks. For > example, fbuf is non-accelerated and VNC does not > support zero-copy transfer, which makes fbuf+vnc have > poor performance. GPU pci passthrough has excellent > performance. But due to its exclusive use, the host > cannot access the GPU anymore, not to mention > supporting multiple VMs. > > I understand why these two designs exist: because > bhyve is part of the base system, we cannot introduce > GPL-licensed software or heavy graphics dependencies. > So it is better, if there is an option, with a minimal > implementation without any heavy dependence, but still > can use modern graphics stack render and display > capabilities, and can support multiple VM. > > My motivation for this proposal stems from my GSoC > work on udmabuf. With the underlying zero-copy buffer > sharing mechanism now in place, I wanted to explore > how bhyve could natively utilize it to overcome the > current performance bottlenecks in graphics rendering > and displaying. > > For rendering, we can implement a device which > presents itself to the guest kernel as a virtio-gpu > device, but does not process any commands internally, > the main virtqueue is handled by a separate userspace > program, vhost-user-gpu. And the device > communicates to vhost-user-gpu using vhost-user > protocol. One implementation of vhost-user-gpu is > rust-vmm's vhost-device-gpu, which processes the data > and sends the rendered image back to QEMU/bhyve for > display, and currently supports gtk and dbus backend as > far as I know. We can then implement a new display > backend, dbus backend, to dispatch the display to > another program, too. But we can't introduce dbus into > the base system, so maybe we need another out-of-tree > small proxy to do the conversion. > > In conclusion, this approach dispatches the actual > rendering and display tasks to two separate programs. > bhyve only presents itself as a virtio-gpu device from the > guest's point of view, and communicates to the two > programs internally. This option is minimal, modular, and > secure, leveraging the modern graphics stack to support > multiple VMs without requiring dedicated hardware > support, while providing the benefits of virtio-gpu. > > I would appreciate any feedback and discussion on the > feasibility of this approach. If the idea is considered > worthwhile, I am willing to invest the time and effort > required to implement it. > > Best, > Zishun Yi Hi, the thing You mentioned is - as much as i like Bhyve - one of the biggest issues with Bhyve - and its really obvious after you migrate from VirtualBox into Bhyve world for example. Personally I would love to see such thing happening - if only You can invest that time - it will not be a wasted time - its very valuable and important thing. Thanks, vermadenhome | help
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