Shared Virtual Addressing (SVA) is the ability to share process address spaces with devices. It is called "SVM" (Shared Virtual Memory) by OpenCL and some IOMMU architectures, but since that abbreviation is already used for AMD virtualisation in Linux (Secure Virtual Machine), we prefer the less ambiguous "SVA".
Sharing process address spaces with devices allows to rely on core kernel memory management for DMA, removing some complexity from application and device drivers. After binding to a device, applications can instruct it to perform DMA on buffers obtained with malloc. The device, buses and the IOMMU must support the following features: * Multiple address spaces per device, for example using the PCI PASID (Process Address Space ID) extension. The IOMMU driver allocates a PASID and the device uses it in DMA transactions. * I/O Page Faults (IOPF), for example PCI PRI (Page Request Interface) or Arm SMMU stall. The core mm handles translation faults from the IOMMU. * MMU and IOMMU implement compatible page table formats. This series requires to support all three features. I tried to facilitate using only a subset of them but enabling it requires more work. Upcoming patches will enable private PASID management, which allows device driver to use an API similar to classical DMA, map()/unmap() on PASIDs. In the future device drivers should also be able to use SVA without IOPF by pinning all pages, or without PASID by sharing the single device address space with a process. Although we don't have any performance measurement at the moment, SVA will likely be slower than classical DMA since it relies on page faults, whereas classical DMA pins all pages in memory. SVA mostly aims at simplifying DMA management, but also improves security by isolating address spaces in devices. Intel and AMD IOMMU drivers already offer slightly differing public functions that bind process address spaces to devices. Because they don't go through an architecture-agnostic API, only integrated devices could use them so far. --- The series adds an SVA API to the IOMMU core, an example implementation (SMMUv3), and an example user (VFIO). Since last version, sent as RFCv2 in October , I reworked the API and fixed some bugs. Patches 1-6 introduce the bind API and track address spaces. This version of the patchset improves documentation, adds device_init()/ shutdown(), and per-bond device driver data. Functions available to device drivers are: iommu_sva_device_init(dev, features, max_pasid) iommu_sva_device_shutdown(dev) iommu_register_mm_exit_handler(dev, handler) iommu_unregister_mm_exit_handler(dev) iommu_sva_bind_device(dev, mm, *pasid, flags, drvdata) iommu_sva_unbind_device(dev, pasid) Patches 7-10 add a generic fault handler. This version reuses the structures introduced by Jacob Pan's vSVA series  (with some changes to match the most recent comments in that thread). Patches 11-36 add complete SVA support to the SMMUv3 driver, for both platform and PCI devices. If you don't care about SMMU I advise to only look at patches 25, 27, 29 and 35, which use the tools introduced earlier. In this version, context code for SMMUv3 moved to a separate module, behind an interface reusable by other IOMMU drivers, and easily extensible for private PASIDs. There are complicated interactions between private and shared contexts (they have a common ASID space), so moving it all to a separate file also helps making sense of refs and locks. Finally, patch 37 adds an ioctl to VFIO providing SVA to userspace drivers. Since last version I fixed a few bugs. You can pull the full series based onto v4.16-rc1+fault patches at: git://linux-arm.org/linux-jpb.git sva/v1 I tested this code on a software model implementing an SMMUv3 and a dummy DMA devices. Any testing report would be greatly appreciated!  [RFCv2 PATCH 00/36] Process management for IOMMU + SVM for SMMUv3 https://www.spinics.net/lists/arm-kernel/msg609771.html  [PATCH v3 00/16] IOMMU driver support for SVM virtualization https://www.spinics.net/lists/kernel/msg2651481.html Jean-Philippe Brucker (37): iommu: Introduce Shared Virtual Addressing API iommu/sva: Bind process address spaces to devices iommu/sva: Manage process address spaces iommu/sva: Add a mm_exit callback for device drivers iommu/sva: Track mm changes with an MMU notifier iommu/sva: Search mm by PASID iommu: Add a page fault handler iommu/fault: Handle mm faults iommu/fault: Let handler return a fault response iommu/fault: Allow blocking fault handlers dt-bindings: document stall and PASID properties for IOMMU masters iommu/of: Add stall and pasid properties to iommu_fwspec arm64: mm: Pin down ASIDs for sharing mm with devices iommu/arm-smmu-v3: Link domains and devices iommu/io-pgtable-arm: Factor out ARM LPAE register defines iommu: Add generic PASID table library iommu/arm-smmu-v3: Move context descriptor code iommu/arm-smmu-v3: Add support for Substream IDs iommu/arm-smmu-v3: Add second level of context descriptor table iommu/arm-smmu-v3: Share process page tables iommu/arm-smmu-v3: Seize private ASID iommu/arm-smmu-v3: Add support for VHE iommu/arm-smmu-v3: Enable broadcast TLB maintenance iommu/arm-smmu-v3: Add SVA feature checking iommu/arm-smmu-v3: Implement mm operations iommu/arm-smmu-v3: Add support for Hardware Translation Table Update iommu/arm-smmu-v3: Register fault workqueue iommu/arm-smmu-v3: Maintain a SID->device structure iommu/arm-smmu-v3: Add stall support for platform devices ACPI/IORT: Check ATS capability in root complex nodes iommu/arm-smmu-v3: Add support for PCI ATS iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops iommu/arm-smmu-v3: Disable tagged pointers PCI: Make "PRG Response PASID Required" handling common iommu/arm-smmu-v3: Add support for PRI iommu/arm-smmu-v3: Add support for PCI PASID vfio: Add support for Shared Virtual Addressing Documentation/devicetree/bindings/iommu/iommu.txt | 24 + MAINTAINERS | 3 +- arch/arm64/include/asm/mmu.h | 1 + arch/arm64/include/asm/mmu_context.h | 11 +- arch/arm64/mm/context.c | 87 +- drivers/acpi/arm64/iort.c | 11 + drivers/iommu/Kconfig | 42 + drivers/iommu/Makefile | 4 + drivers/iommu/amd_iommu.c | 19 +- drivers/iommu/arm-smmu-v3-context.c | 728 +++++++++++ drivers/iommu/arm-smmu-v3.c | 1395 ++++++++++++++++++--- drivers/iommu/io-pgfault.c | 384 ++++++ drivers/iommu/io-pgtable-arm.c | 48 +- drivers/iommu/io-pgtable-arm.h | 67 + drivers/iommu/iommu-pasid.c | 54 + drivers/iommu/iommu-pasid.h | 173 +++ drivers/iommu/iommu-sva.c | 795 ++++++++++++ drivers/iommu/iommu.c | 109 +- drivers/iommu/of_iommu.c | 12 + drivers/pci/ats.c | 17 + drivers/vfio/vfio_iommu_type1.c | 399 ++++++ include/linux/iommu.h | 217 +++- include/linux/pci-ats.h | 8 + include/uapi/linux/pci_regs.h | 1 + include/uapi/linux/vfio.h | 76 ++ 25 files changed, 4381 insertions(+), 304 deletions(-) create mode 100644 drivers/iommu/arm-smmu-v3-context.c create mode 100644 drivers/iommu/io-pgfault.c create mode 100644 drivers/iommu/io-pgtable-arm.h create mode 100644 drivers/iommu/iommu-pasid.c create mode 100644 drivers/iommu/iommu-pasid.h create mode 100644 drivers/iommu/iommu-sva.c -- 2.15.1 _______________________________________________ iommu mailing list firstname.lastname@example.org https://lists.linuxfoundation.org/mailman/listinfo/iommu