Identifying and Eliminating Contention from Booting Concurrent SNP VMs
summary
Concurrent AMD SEV‑SNP guests stall on RMP updates because change_page_attr serializes behind a global CPA lock; removing that lock cuts boot-time contention dramatically in microbenchmarks and thousands of test runs with no crashes. Measured results show a near-linear boot-time rise with concurrent threads and still a 50% increase at 64 updater threads after the change, pointing to remaining pgd_lock hotspots or power/resource limits; prototypes and patches to remove CPA lock and explore per‑PMD locking and staggered RMP updates are prepared.
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chapters (5)
- 0:00Introduction to SMP VMs
- 3:11Investigating RMP update contention
- 5:41Removing the CPA global lock
- 9:36Remaining bottlenecks and solutions
- 10:37Q&A session
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