A good update. The VIRTIO_NET_F_MTU negotiation has been a roadblock for many guest OS implementations on apple's virtualization stack. The spec is vague enough that linux just does it while openbsd had to explicitly patch in support to handle the hypervisor's hardmtu limit.
This is a big deal for local development imho. With the raw single-thread performance of the M4/M5 chips, an openbsd guest is arguably the best environment for testing pf configurations or running isolated mail servers (for example). Being able to rely on viogpu without the black-screen-of-death means we can slowly move away from serial console-only installs for quick VMs.
> With the raw single-thread performance of the M4/M5 chips, an openbsd guest is arguably the best environment for testing pf configurations or running isolated mail servers (for example).
A unikernel would probably be even better? (But then you need a mail server that's set up for running as a unikernel, without an underlying OS.)
Virtualization.framework was introduced in Big Sur. It builds on top of Hypervisor.framework and is essentially Apple's QEMU (in some ways quite literally, it implements QEMU's pvpanic protocol for example). Before QEMU and other VMMs gained ARM64 Hypervisor.framework support, it was the only way to run virtual machines on ARM Macs and still is the only official way to virtualize ARM macOS.
The new Tahoe framework you're probably thinking of is Containerization, which is a WSL2-esque wrapper around Virtualization.framework allowing for easy installation of Linux containers.
Oh good point. I mixed it up, UTM is using qemu under hood, but as someone mentioned now OpenBSD snapshot boots with qemu seemlesly. It's still virtualised though.
My mental model is that each of these covers a different layer of the stack, from lowest to highest:
* hypervisor-framework handles the hypervisor bits, like creating virtual machines, virtualising hardware resources, basically a C API on top of Apple's hypervisor
* virtualization-framework is a higher-level API, meant to make it easy to run a full-blown VM with an OS and hardware integration, without having to reinvent the integration with lower-level primitives that hypervisor-framework provides
* containerization-framework uses virtualization-framework to run Linux containers on macOS in microVMs.
By analogy to not mix them up, it's a bit like KVM > QEMU > containerd.
Maybe I am missing something but the last few times I tested VMs it seemed to end up never shrinking in RAM size once it had grown, is this a real issue and if so is there any improvement coming on that front?
Yes and no; kernels aren’t magic, and “change how this kernel is loaded to match how Linux does it” is actually a reasonable first assignment for an Operating Systems class at a top-tier school. (You’re basically just creating an alternative `main()` if you don’t need a RAM disk image from which to load drivers.)
What, pray tell, would you do for a first assignment in an Operating Systems class at a top-tier school that actually involves making changes to on realistic operating system code?
At the risk of getting further off-topic: what sort of system calls did they have you implement? I’ve never done but a tiny bit of kernel hacking and that sounds like a good exercise, but I’m not sure what would be a good first syscall to add.
My point is that as long as OpenBSD can boot like Linux, you just have to tell whatever VM front-end you’re using that you’re booting a Linux but give it an OpenBSD kernel and RAM disk.
Traditionally BSD has booted very differently than Linux, because Linus adopted the same boot process as MINIX when he first developed it (since he was actually using the MINIX boot blocks at first).
BSD has historically used a bootstrap that understands V7FS/FFS and can load a kernel from a path on it. MINIX takes the actual kernel and RAM disk images as parameters so it doesn’t need to know about filesystems, and that tradition continued with Linux bootstraps once it was standalone.
Parallels will run a VM that can (manually) boot bsd.rd from the EFI shell if you stick BOOTAA64.EFI and bsd.rd on a FAT32 GUID formatted.dmg, connect it to the VM, then boot EFI shell.
Type:
connect -r
map -r
fs0:
bootaa64.efi
boot bin.rd
Then you'll be in the OpenBSD installer, having booted an OpenBSD kernel.
Well done! FreeBSD 15 is a complete no-go for X right now on utm, rdp/vnc is the only way. Hopefully somebody will work out how to get a frame buffer working there, from this.
This is a significant milestone for OpenBSD on Apple hardware. The improved support for Virtualization.framework will definitely make local development and testing much smoother for many users. Kudos to the developers!
Networking is a disappointment but OpenBSD kinda expects you to use the command line. Fire up tmux (included because they invented it) and read the god tier manpages and play some of the games that are included
This is a big deal for local development imho. With the raw single-thread performance of the M4/M5 chips, an openbsd guest is arguably the best environment for testing pf configurations or running isolated mail servers (for example). Being able to rely on viogpu without the black-screen-of-death means we can slowly move away from serial console-only installs for quick VMs.
Big kudos to Helg and Stefan!
A unikernel would probably be even better? (But then you need a mail server that's set up for running as a unikernel, without an underlying OS.)
It started in 7.3 with the frame buffer changes and the only workaround was to disable the kernel driver.
Maybe more people will get to try out OpenBSD successfully now.
The new Tahoe framework you're probably thinking of is Containerization, which is a WSL2-esque wrapper around Virtualization.framework allowing for easy installation of Linux containers.
* hypervisor-framework handles the hypervisor bits, like creating virtual machines, virtualising hardware resources, basically a C API on top of Apple's hypervisor
* virtualization-framework is a higher-level API, meant to make it easy to run a full-blown VM with an OS and hardware integration, without having to reinvent the integration with lower-level primitives that hypervisor-framework provides
* containerization-framework uses virtualization-framework to run Linux containers on macOS in microVMs.
By analogy to not mix them up, it's a bit like KVM > QEMU > containerd.
Hope this helps!
Tested VMs on what? For VMs are used daily and there are, what, hundreds of millions of VMs running as we speak? Billions?
You can look up which top tier schools use it for OS classes.
Traditionally BSD has booted very differently than Linux, because Linus adopted the same boot process as MINIX when he first developed it (since he was actually using the MINIX boot blocks at first).
BSD has historically used a bootstrap that understands V7FS/FFS and can load a kernel from a path on it. MINIX takes the actual kernel and RAM disk images as parameters so it doesn’t need to know about filesystems, and that tradition continued with Linux bootstraps once it was standalone.
You can grab the files from: https://ftp.openbsd.org/pub/OpenBSD/snapshots/arm64/
Actually installing the system is left as an exercise for the reader.