Hi Tom, On Mon, May 06, 2019 at 07:52:02PM +0100, Tom Murphy wrote: > Convert the AMD iommu driver to the dma-iommu api. Remove the iova > handling and reserve region code from the AMD iommu driver. Thank you for your work on this! I appreciate that much, but I am not sure we are ready to make that move for the AMD and Intel IOMMU drivers yet. My main concern right now is that these changes will add a per-page table lock into the fast-path for dma-mapping operations. There has been much work in the past to remove all locking from these code-paths and make it scalable on x86. The dma-ops implementations in the x86 IOMMU drivers have the benefit that they can call their page-table manipulation functions directly and without locks, because they can make the necessary assumptions. The IOMMU-API mapping/unmapping path can't make these assumptions because it is also used for non-DMA-API use-cases. So before we can move the AMD and Intel drivers to the generic DMA-API implementation we need to solve this problem to not introduce new scalability regressions. Regards, Joerg
