Hi Niklas, thanks for the backgrounds. So to sum it up:
The Ubuntu kernel config options for IOMMU_DEFAULT_DMA_LAZY and IOMMU_DEFAULT_DMA_STRICT haven't changed since jammy/22.04: 5.15.0-1.1 to 5.15.0-115.125 CONFIG_IOMMU_DEFAULT_DMA_STRICT=y # CONFIG_IOMMU_DEFAULT_DMA_LAZY is not set 6.8.0-6.6 to 6.8.0-38.38 CONFIG_IOMMU_DEFAULT_DMA_STRICT=y # CONFIG_IOMMU_DEFAULT_DMA_LAZY is not set But with the introduction of c76c067e488c s390/pci: Use dma-iommu layer which moves to a different dma-iommu implementation and 92bce97f0c34 s390/pci: Fix reset of IOMMU software counters (both available since 6.7(rc-1) the IOMMU_DEFAULT_DMA_LAZY kernel config option should be set to 'yes' by default for s390x. Does CONFIG_IOMMU_DEFAULT_DMA_STRICT need to be set to No on top? I don't think so - if lazy is 'yes'. So I believe we can go with 'IOMMU_DEFAULT_DMA_LAZY=y' for s390x only and should be good again. I assume that such situations happen not very often, so it would be ideal if IBM could give us a quick heads-up in such cases (where a kernel config default value for s390x is changed upstream), so that we can double check and potentially take over changes into the Ubuntu config by hand. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2071471 Title: [UBUNTU 24.04] IOMMU DMA mode changed in kernel config causes massive throughput degradation for PCI-related network workloads To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/2071471/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
