Instant Detection of Virtual Devices
summary
Measures mapping PCI config pages into guest MMIO (ECAM/MMCONFIG) to avoid VM exits, add a MMIO direct mapping path that drops ~3,200 PCI config accesses to ~1,000 and cuts PCI init time from 52 ms by ~60–65% (CRX boot <100 ms); add a skip-write heuristic that skips redundant writes for a further ~12% gain; add pre-initialized PCI config written by the hypervisor before boot for another ~2% gain, ending with roughly 300 trapped accesses and ~78–80% total reduction in device init cost.
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chapters (8)
- 0:00Introduction to talk
- 0:26Importance of kernel boot time
- 3:25Problem with PCI device initialization
- 7:43MMIO direct read solution
- 12:23Skip write optimization
- 13:48Pre-initialized PCI config
- 15:58Performance improvements summary
- 24:12Audience Q&A discussion
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