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I have an Intel CPU and no discrete GPU, running latest Windows 11 insider.

when I create a VM with Hyper-V, this is what I see in device manager for GPU:

enter image description here

And when I launch Windows Sandbox, this is what the device manager looks like:

enter image description here

even though not only my system lacks discrete GPU but also uses an integrated old GPU, Windows Sandbox still passes through my GPU and I can use graphic intensive programs in Windows Sandbox with no problem at all, such as Photoshop 2022's neutral filters or Luminar Neo.

my question is, how does Windows Sandbox manage to do this? (which is very impressive imo). it obviously uses the same virtualization technology as Hyper-V, so why Hyper-V doesn't let me use my IGPU in VM and only requires server graphic cards like Nvidia Quadro or AMD Fire pro to use with DDA (Discrete Device Assignment) which only works in Windows Server's Hyper-V.

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  • @John I wasn't. this is how Host device manager looks like: imgur.com/a/ui2uZu4 Which version/build of Windows are you running? what's your IGPU?
    – user1670677
    Aug 13, 2022 at 21:55

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Intel GPUs also have a virtualization technology just like AMD and nVidia GPUs do. Unlike the latter, though, Intel includes the "GVT-g" feature in all GPUs as standard.

This isn't exactly the same as Direct Device Assignment though. DDA can only move whole PCI devices from host to a guest – this works with server GPUs because they appear as multiple virtual PCI devices, one for each host or guest OS.

Meanwhile your GPU is just one PCI device, so it can't be given to a VM via DDA simply because it's already in use by the host. (But not because it's integrated – even though it's physically inside the CPU package, it's still just a normal PCI device.) Instead, GVT-g requires some cooperation between the host GPU driver and the hypervisor to assign resources.

I actually don't know whether Windows Sandbox uses GVT-g but I expect it would; this seems to be the main reason for its WDDM 2.5 driver requirement.

But alternatively, Windows Sandbox could be doing something similar to VirtualBox's 3D acceleration mode and creating a virtual device that just forwards the DirectX commands to the host device. (I think that's how RemoteFX used to work in the past? Both RemoteFX and VirtualBox's previous 3D accel mode were removed due to security issues, but a more limited version would be possible.)

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  • Thanks, just found out that support for GVT-g ended since 11 gen Intel CPUs in favor of SR-IOV (Single Root IO Virtualization) (mine is 7th gen). also in DXDIAG in WS, WDDM version is 1.3 but on the host it's version 3.0. so with these info and screenshots above, would you say I'm using Windows Advanced Rasterization Platform (WARP) or the new WDDM GPU virtualization in Windows Sandbox? do any of them use the old RemoteFX technology? docs.microsoft.com/en-us/windows/security/threat-protection/…
    – user1670677
    Aug 13, 2022 at 22:12
  • RemoteFX support was discontinued nearly a decade ago. The feature was literally removed nearly 5 years ago.
    – Ramhound
    Aug 13, 2022 at 22:43

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