Re:Why Xen Wasn't Hit by RETBleed on Intel CPUs
by plam503711 on Friday August 26, 2022 @03:09PM
(#32611485)
Xen Project is far being dead (there's a lot of activity in the mailing list, and now, thanks to new contributors like Vates/XCP-ng, there's also more initiatives to have a decent project tracking, see https://gitlab.com/groups/xen-project/-/epics?state=opened&p... for example).
Regarding nested virt, you are mostly right: it's only "working-ish" for basic things, but indeed, it's broken when you start to use anything heavy in your nested VM. The main reason nobody fixed it is because it's not really used: as any other open source project, you find what you need if you contribute. Obviously, as soon someone will need this and willing to contribute, it will change :)
To name one example, nested virtualization support is not only hopelessly broken, it's MORE broken in recent releases than it was a decade ago. You can see right here how the feature kept getting broken by every other release until nothing worked anymore: https://wiki.xenproject.org/wiki/Nested_Virtualization_in_Xe....
And Xen is literally the only virtualizer out there that does not support nested virtualization, which is a rather critical feature since many (dev) stacks assume one has hardware virtualization, and Windows is going to require it sooner than later.