Nested Virtualization (X86) Part II

on YouTube ↗30m

" summary

Sketch implementation exists for nested x86 on Xen with a working VMcb/PTM plumbing but concrete pitfalls appear: inconsistent naming across vmcS/vmcb variants, new feature leakage where PCID bits cause VM entry failure (L0 copies PCID-bearing CR3 into VMcb02 and the hardware rejects the entry, crashing L2), and naive VMEXIT handling that sometimes should GP-fault instead of letting L2 directly affect L0. Planned work: XTF unit tests, add MSR/CPUID filtering for nested guests, and apply shadow-paging optimizations to PTM shadowing.

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" chapters (7)

1. 0:00Introduction and review
2. 1:49Naming pitfalls in code
3. 3:56New feature leakage issue
4. 10:08Naive vmexit handling
5. 11:55Future work and testing
6. 13:18Optimizing PTM shadowing
7. 29:05Q&A session

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