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Yes > ACS overrides on the > command line would need to be enforced between the original and kexec > kernel such that IOMMU groups are deterministic. Thanks, That's a good point, I think as a reasonable starting point we should require live update preserved devices to have singleton iommu_groups on both sides. That is easy to check and enforce, and it doesn't matter how the administrator makes that happen. You also can't change the ACS flags while traffic is flowing because that changes the fabric routing too. This should take care to enforce that restriction as well. Jason