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Set iommu=pt on the amd variant - #50
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DMA from the GPUs then skips IOMMU address translation, which AMD's ROCm docs recommend for multi-GPU hosts. The argument goes in /usr/lib/bootc/kargs.d/50-sibyl-amd.toml, as nvidia's kargs do. The cost is that a rogue PCIe or Thunderbolt device can read all memory. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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The change
os/variants/sibyl-amd-kargs.tomlsets the kernel argumentiommu=pton x86_64. The amd build installs it as/usr/lib/bootc/kargs.d/50-sibyl-amd.toml, the same way that the nvidia variant installs its kernel arguments.iommu=pt, DMA from the devices that the host owns skips IOMMU address translation. AMD's ROCm docs recommend it for multi-GPU hosts. The IOMMU stays on for devices that a VM gets.Verification
kargs.d, andbootc container lintpasses 14 checks.rpm-ostree kargs --append-if-missing=iommu=ptadded the argument to the staged deployment. It takes effect at the next reboot. The reboot waits until a training run ends.🤖 Generated with Claude Code