Some modern accelerators such as Intel's Data Streaming Accelerator (DSA) require PASID in DMA requests to be operational. Specifically, the work submissions with ENQCMD on shared work queues require PASIDs. The use cases include both user DMA with shared virtual addressing (SVA) and in-kernel DMA similar to legacy DMA w/o PASID. Here we address the latter.
DMA mapping API is the de facto standard for in-kernel DMA. However, it operates on a per device or Requester ID(RID) basis which is not PASID-aware. To leverage DMA API for devices relies on PASIDs, this patchset introduces the following APIs 1. A driver facing API that enables DMA API PASID usage: iommu_attach_dma_pasid(struct device *dev, ioasid_t &pasid); 2. VT-d driver default domain op that allows attaching device-domain-PASID Once PASID DMA is enabled and attached to the appropriate IOMMU domain, device drivers can continue to use DMA APIs as-is. There is no difference in terms of mapping in dma_handle between without PASID and with PASID. The DMA mapping performed by IOMMU will be identical for both requests, let it be IOVA or PA in case of pass-through. In addition, this set converts DSA driver in-kernel DMA with PASID from SVA lib to DMA API. There have been security and functional issues with the kernel SVA approach: (https://lore.kernel.org/linux-iommu/20210511194726.gp1002...@nvidia.com/) The highlights are as the following: - The lack of IOTLB synchronization upon kernel page table updates. (vmalloc, module/BPF loading, CONFIG_DEBUG_PAGEALLOC etc.) - Other than slight more protection, using kernel virtual address (KVA) has little advantage over physical address. There are also no use cases yet where DMA engines need kernel virtual addresses for in-kernel DMA. Subsequently, cleanup is done around the usage of sva_bind_device() for in-kernel DMA. Removing special casing code in VT-d driver and tightening SVA lib API. This work and idea behind it is a collaboration with many people, many thanks to Baolu Lu, Jason Gunthorpe, Dave Jiang, and others. ChangeLog: v4 - Rebased on "Baolu's SVA and IOPF refactoring" series v6. (https://github.com/LuBaolu/intel-iommu/commits/iommu-sva-refactoring-v6) - Fixed locking for protecting iommu domain PASID data - Use iommu_attach_device_pasid() API instead of calling domain ops directly. This will leverage the common pasid_array that replaces driver specific storage in device_domain_info. - Added a helper function to do look up in pasid_array from domain v3 - Rebased on "Baolu's SVA and IOPF refactoring" series v5. (https://github.com/LuBaolu/intel-iommu/commits/iommu-sva-refactoring-v5) This version is significantly simplified by leveraging IOMMU domain ops, attach_dev_pasid() op is implemented differently on a DMA domain than on a SVA domain. We currently have no need to support multiple PASIDs per DMA domain. (https://lore.kernel.org/lkml/20220315142216.gv11...@nvidia.com/). Removed PASID-device list from V2, a PASID field is introduced to struct iommu_domain instead. It is intended for DMA requests with PASID by all devices attached to the domain. v2 - Do not reserve a special PASID for DMA API usage. Use IOASID allocation instead. - Introduced a generic device-pasid-domain attachment IOMMU op. Replaced the DMA API only IOMMU op. - Removed supervisor SVA support in VT-d - Removed unused sva_bind_device parameters - Use IOMMU specific data instead of struct device to store PASID info *** SUBJECT HERE *** *** BLURB HERE *** Jacob Pan (6): iommu: Add a per domain PASID for DMA API iommu: Add a helper to do PASID lookup from domain iommu/vt-d: Implement domain ops for attach_dev_pasid iommu: Add PASID support for DMA mapping API users dmaengine: idxd: Use DMA API for in-kernel DMA with PASID iommu/vt-d: Delete unused SVM flag drivers/dma/idxd/idxd.h | 1 - drivers/dma/idxd/init.c | 34 +++-------- drivers/dma/idxd/sysfs.c | 7 --- drivers/iommu/dma-iommu.c | 114 ++++++++++++++++++++++++++++++++++++ drivers/iommu/intel/iommu.c | 72 ++++++++++++++++++++++- drivers/iommu/intel/svm.c | 2 +- drivers/iommu/iommu.c | 22 +++++++ include/linux/dma-iommu.h | 3 + include/linux/intel-svm.h | 13 ---- include/linux/iommu.h | 8 ++- 10 files changed, 226 insertions(+), 50 deletions(-) -- 2.25.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
