Records the 2026-10-18 answer to 'does a recent kernel change retire
amd_iommu=off': PerfOpt (iommu tree 2026-09-24, Linux 7.4) stops GPA->SPA
translation for the privileged iGPU while the IOMMU stays enabled for every
other device, the NPU included. Local census proves the fix is absent here
(zero perfopt symbols in System.map-7.0.0-38, archive caps at 7.0.0-38.38),
and the September 13-16% figure was translated-domain cost, not strict-flush
cost -- lazy DMA is the Ubuntu default, so iommu=pt already avoids it. The
corrected procedure therefore flips to iommu=pt now and treats PerfOpt as a
2-4% later bonus on this silicon class (Phoronix desktop arm), with the NPU
legal under identity mode because amdxdna binds its own SVA domain.
Re-keys the AGENTS.md key-lesson bullet; no host change.
Frank
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