Sadly, as you can tell, they have not taken me up on my requests. Awesome that other people got it working!
What exactly do you feel macOS is missing?
> I have been bothering the VM team for years for VM GPU pass through.
Good luck. I'm sure they're keen on giving people access to this so that people can spend their money on NVIDIA GPUs instead of buying more expensive Macs. :)
Would of course be awesome, but I'd be very surprised if it happened.
(Meanwhile, I'm recompiling Wine to see if I can patch it to address an issue that was hotfixed in Proton two weeks ago but isn't in a CrossOver build yet, so yeah, there's maybe some arguments to be made here that I'd be a potential beneficiary. If I weren't too cheap to spring for an eGPU in today's market, anyway.)
The VFIO-style driver made by the author of this also appears generic enough to support all kinds of PCIe, not just GPUs. Apple might find a way to weasel out of this ("hey, this is for hardware companies and you don't seem to be affiliated with one", "your driver requests too broad access", etc.) if there really is a conflict of interest, but so far, there's a chance it will just get rubber-stamped.
I can see them rejecting it for legitimate reasons, though, at least as far as "legitimate" with Apple goes. This driver is essentially a thin layer over PCIDriverKit, exposing all functionality that's supposed to be behind the entitlement to arbitrary applications, in similar fashion to WinRing0. They probably didn't come up with all this bureaucracy only to sign something like that in the end. We'll see what happens.
[0] https://github.com/scottjg/qemu-vfio-apple/blob/84ecdcf5db6b...
[1] https://developer.apple.com/documentation/pcidriverkit/creat...
Presumably with the right entitlements you can just hit the same (presumably IOKit) syscalls that driverkit does. But that's an extra layer of reverse engineering, and you're not really using driverkit anymore.
i don't think the issues with the project really are specific to driverkit.
1. Virtualization.framework seems to support some form of GPU passthrough from the host (granted, not eGPU - it's for the integrated GPU). I think the primary use case is having macOS guests get acceleration, while still sharing GPU time with the host. There is also a patch that recently hit QEMU mainline that supports using the "venus server" with virtio-gpu to support a similar functionality for Linux guests under Hypervisor.framework.
2. Apple internally has some kind of PCI Passthrough support available in Virtualization.framework. It seems like the code is shipped to customers in the framework, but it relies on some kind of kext or kernel component that isn't shipped in retail macOS. I can't say if that's intended to ever be released to customers, but clearly someone at Apple has thought about this the feature.
Unless there's another method I missed, the internal GPU "pass through" of Virtualization.framework you're thinking of might actually just be paravirualization, at least that's what the name suggests. It's implemented in the public ParavirtualizedGraphics framework [0], albeit for PG on Arm macOS, the relevant interfaces are private [1]. I haven't looked that deep into it per se, but, fixing the bugs around it, I've run into a few clues suggesting that it's just a command stream + shared memory being passed around. It also uses its own generic driver on the guest side.
Great job, by the way! Love how authors of pieces like this casually come here to comment :)
[0] https://developer.apple.com/documentation/paravirtualizedgra...
[1] https://github.com/qemu/qemu/blob/edcc429e9e41a8e0e415dcdab6...
there also appears to be a generic pci passthrough path. we were discussing it on the qemu-devel list: https://lore.kernel.org/qemu-devel/C35B5E97-73F2-4A60-951B-B...
There's some randomness around Tahoe for FileVault and it crashing because Data is detected as not encrypted (and that's not OK on bare metal). If hitting that case you might need to enable FileVault inside the VM (and remember to sync aux storage afterwards if not done)
I see the author of this patch set has run into a few similar issues as me. Strangely, not all of them: I don't see patches for the new PCI MSI-X device introduced somewhere in Sequoia (IIRC), a source of kernel panics for me; and there's still a bug in the PG MMIO path that casts all writes to 32-bit, this one caused me a lot of headaches (no errors but no video adapter detected). I'm somewhat surprised to hear that this works!
There's two significant problems that we both have came across:
- LLVM now favoring pre-indexed load/stores which trap with ISV=0 for MMIO accesses, and those ending up in the GIC initialization path of the newer macOS kernels (looks like there's a separate patch set for this [0]),
- Hypervisor.framework trapping PAC HVC calls.
It seems like the latter has been worked around here by signing QEMU with an Apple-private entitlement and running with SIP off, but there's actually a different way! While some HVCs are trapped right in the host kernel, the PAC trapping happens within Hypervisor.framework itself (at least in the host OSes I tested). It's possible to patch out this functionality without special privileges or talk to the in-kernel hypervisor directly. I originally tested with the former, and chose to implement the latter as a separate accel in the code I was planning to submit upstream, but the complexity of it exploded and, besides confirming that it would have worked, I haven't managed to finish my implementation.
Does the Tahoe crash you mentioned manifest itself in stage 2 iBoot panics? I must admit 26 was never quite my priority so I haven't looked into it, but if so, it might have been closer to booting than I thought :)
[0] https://lists.nongnu.org/archive/html/qemu-devel/2026-04/msg...
The userspace reboot after FileVault password entry acts a bit oddly with QEMU input devices so you might need to attach a new USB tablet or kbd from the monitor.
> looks like there's a separate patch set for this
Yup and it's a bit of a problem to figure out the right thing to do for it on the upstreaming side as normal guests aren't supposed to do that.
> It's possible to patch out this functionality without special privileges or talk to the in-kernel hypervisor directly
Or pre-patch them all to HVC #1 works too. Patching the host Hypervisor.framework sounds quite brittle especially after they moved to a pile of C++
Ah, must be something else then.
> normal guests aren't supposed to do that
Oh how I wish Arm didn't let anything like this slip into the architecture spec to begin with! Massive source of pain, especially with protected memory/CCA guests. It's not macOS triggering this in isolation either. Most start up binaries for QNX do this too, somehow also in the GIC init path.
I've looked at how different hypervisors/VMMs handle this and, if this makes that patch set any less hacky, Virtualization.framework, QNX Hypervisor, and (I think) VMware all decode and emulate those instructions in software. Virtualization.framework is a remarkable spaghetti in this regard :)
> Or pre-patch them all to HVC #1 works too. Patching the host Hypervisor.framework sounds quite brittle especially after they moved to a pile of C++
Possibly! IIRC, if HCR_EL2.HCD==1, HVC should trap as undefined instruction. Not sure how much of HCR_EL2 can be set from the user-space, but perhaps this could be the least invasive way.
Simply ignoring the instruction, though, is not enough. I remember in my setup, with HVC handling stubbed out, secondary cores would always fail to start. I suspect this to be the culprit.
The SMP bring-up code would fail to pass pointer authentication on the first indirect branch. It would then immediately pivot into FLEH->SLEH->panic(). panic() shortly would attempt to make an indirect jump itself, hoping to crash the other processors, but instead, getting stuck in a loop of calling itself. This would eventually get caught by a stack overflow guard somewhere in FLEH/SLEH, which would place the core in an infinite loop, and... the system would continue to run with just the boot core. Yo dawg, I heard you like panics :)
That's not ideal because of:
> Any resulting exception is taken to the Exception level at which the HVC instruction is executed.
instead of trapping to the hypervisor
> I've looked at how different hypervisors/VMMs handle this and, if this makes that patch set any less hacky, Virtualization.framework, QNX Hypervisor, and (I think) VMware all decode and emulate those instructions in software. Virtualization.framework is a remarkable spaghetti in this regard :)
And so does Hyper-V.
> It's not macOS triggering this in isolation either
There are some nightmare cases that SEPOS specifically triggers, such as doing isv=0 accesses to GICR... when using the Apple vGIC handling _that_ becomes truly bizarre.
> Simply ignoring the instruction, though, is not enough
Yeah that's not a great idea
My bad! I mean, ehh, I guess you could maintain a breakpoint in the guest kernel's exception vector table or have QEMU inject its own "zero-level exception handler" whose only purpose would be to capture those HVCs, but that's not as straightforward as I originally thought. And since those PAC calls are expected to set a few Apple-specific registers anyway, using the entitlement or skipping Hypervisor.framework and talking straight to the kernel seem like the only viable options when macOS is the guest.
> There are some nightmare cases that SEPOS specifically triggers, such as doing isv=0 accesses to GICR... when using the Apple vGIC handling _that_ becomes truly bizarre.
Interesting! Are there any resources out there about virtualizing sepOS?
> whose only purpose would be to capture those HVCs
quite expensive because you get to trap ~ all EL0 -> EL1 priv transitions through the virtualisation infrastructure as the sync handler has a lot going through it
Figuring out where to put it and how to keep it mapped is another problem, though!
Anyway, the Mac Pro is dead now. There's only so much sales audio and video professionals can provide.
I don’t know about that. Apple supported some full size GPUs in past product lines and the number of users was very small. Granted, LLMs change that demand but the audience for Mac Pro buyers who would use a full-size GPU that is impossible to obtain is almost nothing compared to their laptop sales.
Part of the reason the new Mac Pro failed to find an audience can definitely be blamed on macOS' hostility to third party hardware. Who knows what Apple would be worth if they beat Nvidia's Grace CPU to the datacenter market. It was certainly their opportunity.
Admittedly… what’s on my desk? A MacBook M4 Air, a Mac Studio, and there’s an x86 iMac in the corner.
What goes in the travel bag? A MacBook Pro or the Air.
Every time I look at buying something else the math doesn’t add up.
The 5090 sits in a commodity PC chassis. It’s not like I need a model running on my own computer.
The only ones left were people like John Siracusa that still hoped to the very last minute, that Apple would change their mind.
Maybe it doesn’t matter that much now because they’ve literally exited all the businesses where an external GPU is going to matter. But sticking with AMD all that time out of spite is just wild.
It isn't only audio and video.
https://www.reddit.com/r/hardware/comments/1hmgmuf/apples_hi...
Things have moved on since the days where GPUs in Macs were a priority.
But then the AI race has changed things. So who knows - maybe we will one day see official eGPU support from Apple and new drivers from nVidia. Wouldn't put on money on it though....
Arguably more petty. SJ has been dead for almost 15 year now, I imagine the C-suite might get over it at some point.
I can believe it. IIRC Jobs also snubbed ATI once after they leaked the GPUs going in the next PowerMac model.
Not at Apple. They have a looooooong institutional memory that's passed down. They're still pissed at Gizmodo. I'm shocked they made a deal with Intel. I think if it hadn't been for the global political uncertainty right now they would not have signed that fab deal with Intel.
Will Apple ever make a computer that makes Siracusa happy? (and do you have the "Believe" shirt?)
Now they gave up on the workstation market that really enjoys their slots for all myriad of cards.
Having a thunderbolt cable salad is only for those that miss external extensions from 8 and 16 bit home computer days.
Which is clearly what Apple is nowadays focused, if you look back at the vertical integrations before the PC clones market took off.
So now if you really need a workstation, it is either Windows, or one of those systems sold with Red-Hat Enterprise/Ubuntu from IBM, Dell , HP.
I haven’t seen a non-laughable workstation config from the big vendors since the dot com bubble. Presumably they exist, I guess?
I've been pretty darn happy with the Puget Systems custom workstation I ordered last year before the memory craze started (especially since it has 192GiB of DDR5).
I also ordered another family member a custom "Tiki" system from Falcon Northwest and that has also been quite excellent from what I've seen and they've told me.
Now is obviously not the most economical time to order a new system, but when it is appropriate (and for what it's worth) I think those are two great system builders.
The last I checked, the really big players tended to add value add gimmicks (water cooling is a common one, custom psu form factors are another) with reliability / compatibility issues. That’s the tier to avoid, not the Puget systems of the world.
My Puget Systems workstation for example has a simple AIO for cooling with some Noctua fans and a Fractal Design 7 XL full tower case.
The Tiki system I ordered for a family member from Falcon Northwest does have a custom case, but almost everything else is fairly standard inside. The super small form factor was important to them.
Could I have built either of these systems myself? Absolutely -- I've done that for at least prior 20 years or so, and I've built dozens for employers, but it sure was nice to buy one that just worked this time instead of having to having to fiddle with memory sticks or find exactly the right bios settings for stability, etc.
I'm well aware of the premium I paid but I can honestly say it has been incredibly nice to have a workstation that just works without having to fiddle with bios updates or hardware. I also don't really have the time to spare so I was entirely willing to trade funds for time.
It is too inefficient to design a machine which _might_ have two GPU and a flock of additional drives installed into it. It just makes sense to instead design around having independent hardware in its own case, which can meet its own power/cooling needs. This has been a design goal since the trashcan Mac.
Having a PCIe bus increases bandwidth and reduces latency, but once you account for eGPU and for people who would be happy building custom solutions on platforms other than macOS, there's likely not enough identified market for a modular design.
Even if the drivers loaded, they can't talk to the GPU from within docker (unless one implements PCI passthrough). MacOS owns the PCI bus in this scenario.