Nested Virtualization of Windows Hyper-V on XCP-ng
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@Chuckz Why do you need Core Isolation enabled in a VM? Core Isolation is designed to protect processes within Windows 11 by using VBS, if you're already isolating the VM I don't see a huge reason to have it enabled.
It's worth noting again that Microsoft themselves says to NOT use Nested Virt for production use, very specifically in their own documentation.
I get what you're wanting here but reality is 99% of places don't need nested virtualization and if they do they should probably rethink it since it's not considered stable or production ready on ANY hypervisor. This isn't specific to XCP-ng.
Hyper-V has probably the best nested virt support and even they say it should not be used in production environments.
I'm not saying I don't want this feature to work better, I do. But I can't imagine it should be a priority for Vates or anyone working on Xen because it's not really needed for production setups.
If I am missing some reason you have to have this enabled please let me know, but virtualizing Windows just to nest another Windows so you can enable Core Isolation is really cumbersome and not worth any benefits it provides as far as I can tell.
Hi @planedrop Sure, I agree the isolation that XCP-ng's Xen hypervisor provides protection of other guests on the host from a compromised Windows guest, but it won't protect the confidential data and other services provided by that compromised Windows guest. Nor will it protect the other hosts on the network from attacks that can spread laterally via the network rather than via security holes between different guests on the host. The hypervisor is only one piece of the security process, it is not enough. So I want to protect that Windows guest from attacks that could have been stopped with core isolation, because I don't want even a single device or guest in my infrastructure compromised.
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I'm not saying I don't want this feature to work better, I do. But I can't imagine it should be a priority for Vates or anyone working on Xen because it's not really needed for production setups.
I respectfully disagree. This should be a priority for Vates and Xen because currently, neither Vates nor Xen can provide the core isolation feature for their Windows guests. I think it is a mistake to think the isolation that Xen / Vates / XCP-ng provides between guests on a XCP-ng host can provide the same level of security for a Windows guest that the core isolation feature that nested Hyper-V can provide for that Windows guest.
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@Chuckz wouldn't the better solution here be to prioritize making Core Isolation work within XCP-ng guests rather than focusing on nested virtualization?
Nested virt has other issues and again should not really be used with high priority VMs.
I guess that's the whole thing I'm getting at, nested virt isn't the fix for this specific issue.
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That's interesting. Microsoft's Enterprise Connected Cache is a containerized setup on Linux containers, however the installer is only available for Windows. Running Linux-based containers requires nested virtualization.
This is what got me wondering about nested virtualization support for XCP-ng.
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@Byte0 I think this is a fair use case, containers are a bit different and what you described is basically how containers work on most setups. I mean K8s on XCP-ng works that way, you deploy VMs which then have containers running inside them.
So not quite the same as nested virt.
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@Chuckz wouldn't the better solution here be to prioritize making Core Isolation work within XCP-ng guests rather than focusing on nested virtualization?
Nested virt has other issues and again should not really be used with high priority VMs.
I guess that's the whole thing I'm getting at, nested virt isn't the fix for this specific issue.
@planedrop That would be cool if core isolation could work directly in XCP-ng guests without help of nested Hyper-V. I already asked @stormi if this is possible in earlier post today:
Chuckz said:
Does XCP-ng support core isolation in Windows 11 guests via some mechanism other than by nested virtualization? I presume that I cannot get core isolation to work in Windows guests because of lack of NV support in Xen.
So far no reply to that question but I only asked earlier today. I presume it is a complex technical question that cannot be answered without discussion with upstream Xen developers.
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