Linaro-mm-sig September 2025

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[PATCH v1 00/10] vfio/pci: Allow MMIO regions to be exported through dma-buf

by Leon Romanovsky

Changelog: v1: * Changed commit messages. * Reused DMA_ATTR_MMIO attribute. * Returned support for multiple DMA ranges per-dMABUF. v0: https://lore.kernel.org/all/cover.1753274085.git.leonro@nvidia.com --------------------------------------------------------------------------- Based on "[PATCH v1 00/16] dma-mapping: migrate to physical address-based API" https://lore.kernel.org/all/cover.1754292567.git.leon@kernel.org series. --------------------------------------------------------------------------- This series extends the VFIO PCI subsystem to support exporting MMIO regions from PCI device BARs as dma-buf objects, enabling safe sharing of non-struct page memory with controlled lifetime management. This allows RDMA and other subsystems to import dma-buf FDs and build them into memory regions for PCI P2P operations. The series supports a use case for SPDK where a NVMe device will be owned by SPDK through VFIO but interacting with a RDMA device. The RDMA device may directly access the NVMe CMB or directly manipulate the NVMe device's doorbell using PCI P2P. However, as a general mechanism, it can support many other scenarios with VFIO. This dmabuf approach can be usable by iommufd as well for generic and safe P2P mappings. In addition to the SPDK use-case mentioned above, the capability added in this patch series can also be useful when a buffer (located in device memory such as VRAM) needs to be shared between any two dGPU devices or instances (assuming one of them is bound to VFIO PCI) as long as they are P2P DMA compatible. The implementation provides a revocable attachment mechanism using dma-buf move operations. MMIO regions are normally pinned as BARs don't change physical addresses, but access is revoked when the VFIO device is closed or a PCI reset is issued. This ensures kernel self-defense against potentially hostile userspace. The series includes significant refactoring of the PCI P2PDMA subsystem to separate core P2P functionality from memory allocation features, making it more modular and suitable for VFIO use cases that don't need struct page support. ----------------------------------------------------------------------- The series is based originally on https://lore.kernel.org/all/20250307052248.405803-1-vivek.kasireddy@intel.c… but heavily rewritten to be based on DMA physical API. ----------------------------------------------------------------------- The WIP branch can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/log/?h=… Thanks Leon Romanovsky (8): PCI/P2PDMA: Remove redundant bus_offset from map state PCI/P2PDMA: Separate the mmap() support from the core logic PCI/P2PDMA: Simplify bus address mapping API PCI/P2PDMA: Refactor to separate core P2P functionality from memory allocation PCI/P2PDMA: Export pci_p2pdma_map_type() function types: move phys_vec definition to common header vfio/pci: Enable peer-to-peer DMA transactions by default vfio/pci: Add dma-buf export support for MMIO regions Vivek Kasireddy (2): vfio: Export vfio device get and put registration helpers vfio/pci: Share the core device pointer while invoking feature functions block/blk-mq-dma.c | 7 +- drivers/iommu/dma-iommu.c | 4 +- drivers/pci/p2pdma.c | 154 ++++++++---- drivers/vfio/pci/Kconfig | 20 ++ drivers/vfio/pci/Makefile | 2 + drivers/vfio/pci/vfio_pci_config.c | 22 +- drivers/vfio/pci/vfio_pci_core.c | 59 +++-- drivers/vfio/pci/vfio_pci_dmabuf.c | 390 +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_priv.h | 23 ++ drivers/vfio/vfio_main.c | 2 + include/linux/dma-buf.h | 1 + include/linux/pci-p2pdma.h | 114 +++++---- include/linux/types.h | 5 + include/linux/vfio.h | 2 + include/linux/vfio_pci_core.h | 4 + include/uapi/linux/vfio.h | 25 ++ kernel/dma/direct.c | 4 +- mm/hmm.c | 2 +- 18 files changed, 715 insertions(+), 125 deletions(-) create mode 100644 drivers/vfio/pci/vfio_pci_dmabuf.c -- 2.50.1

11 months

[PATCH v11 0/9] TEE subsystem for protected dma-buf allocations

by Jens Wiklander

Hi, This patch set allocates the protected DMA-bufs from a DMA-heap instantiated from the TEE subsystem. The TEE subsystem handles the DMA-buf allocations since it is the TEE (OP-TEE, AMD-TEE, TS-TEE, or perhaps a future QTEE) which sets up the protection for the memory used for the DMA-bufs. The DMA-heap uses a protected memory pool provided by the backend TEE driver, allowing it to choose how to allocate the protected physical memory. The allocated DMA-bufs must be imported with a new TEE_IOC_SHM_REGISTER_FD before they can be passed as arguments when requesting services from the secure world. Three use-cases (Secure Video Playback, Trusted UI, and Secure Video Recording) have been identified so far to serve as examples of what can be expected. The use-cases have predefined DMA-heap names, "protected,secure-video", "protected,trusted-ui", and "protected,secure-video-record". The backend driver registers protected memory pools for the use-cases it supports. Each use-case has its own protected memory pool since different use-cases require isolation from different parts of the system. A protected memory pool can be based on a static carveout instantiated while probing the TEE backend driver, or dynamically allocated from CMA (dma_alloc_pages()) and made protected as needed by the TEE. This can be tested on a RockPi 4B+ with the following steps: repo init -u https://github.com/jenswi-linaro/manifest.git -m rockpi4.xml \ -b prototype/sdp-v11 repo sync -j8 cd build make toolchains -j$(nproc) make all -j$(nproc) # Copy ../out/rockpi4.img to an SD card and boot the RockPi from that # Connect a monitor to the RockPi # login and at the prompt: gst-launch-1.0 videotestsrc ! \ aesenc key=1f9423681beb9a79215820f6bda73d0f \ iv=e9aa8e834d8d70b7e0d254ff670dd718 serialize-iv=true ! \ aesdec key=1f9423681beb9a79215820f6bda73d0f ! \ kmssink The aesdec module has been hacked to use an OP-TEE TA to decrypt the stream into protected DMA-bufs which are consumed by the kmssink. The primitive QEMU tests from previous patch sets can be tested on RockPi in the same way using: xtest --sdp-basic The primitive tests are tested on QEMU with the following steps: repo init -u https://github.com/jenswi-linaro/manifest.git -m qemu_v8.xml \ -b prototype/sdp-v11 repo sync -j8 cd build make toolchains -j$(nproc) make SPMC_AT_EL=1 all -j$(nproc) make SPMC_AT_EL=1 run-only # login and at the prompt: xtest --sdp-basic The SPMC_AT_EL=1 parameter configures the build with FF-A and an SPMC at S-EL1 inside OP-TEE. The parameter can be changed to SPMC_AT_EL=n to test without FF-A using the original SMC ABI instead. Please remember to do %make arm-tf-clean for TF-A to be rebuilt properly using the new configuration. https://optee.readthedocs.io/en/latest/building/prerequisites.html list dependencies required to build the above. The primitive tests are pretty basic, mostly checking that a Trusted Application in the secure world can access and manipulate the memory. There are also some negative tests for out of bounds buffers, etc. Thanks, Jens Changes since V10: * Changed the new ABI OPTEE_MSG_CMD_GET_PROTMEM_CONFIG to report a list of u32 memory attributes instead of u16 endpoints to make room for both endpoint and access permissions in each entry. * In "tee: new ioctl to a register tee_shm from a dmabuf file descriptor", remove the unused path for DMA-bufs allocated by other means than the on in the TEE SS. * In "tee: implement protected DMA-heap", handle unloading of the backend driver module implementing the heap. The heap is reference counted and also calls tee_device_get() to guarantee that the module remains available while the heap is instantiated. * In "optee: support protected memory allocation", use dma_coerce_mask_and_coherent() instead of open-coding the function. * Added Sumit's R-B to - "optee: smc abi: dynamic protected memory allocation" - "optee: FF-A: dynamic protected memory allocation" - "optee: support protected memory allocation" - "tee: implement protected DMA-heap" - "dma-buf: dma-heap: export declared functions" Changes since V9: * Adding Sumit's R-B to "optee: sync secure world ABI headers" * Update commit message as requested for "dma-buf: dma-heap: export declared functions". * In "tee: implement protected DMA-heap": - add the hidden config option TEE_DMABUF_HEAPS to tell if the TEE subsystem can support DMA heaps - add a pfn_valid() to check that the passed physical address can be used by __pfn_to_page() and friends - remove the memremap() call, the caller is should do that instead if needed * In "tee: add tee_shm_alloc_dma_mem()" guard the calls to dma_alloc_pages() and dma_free_pages() with TEE_DMABUF_HEAPS to avoid linking errors in some configurations * In "optee: support protected memory allocation": - add the hidden config option OPTEE_STATIC_PROTMEM_POOL to tell if the driver can support a static protected memory pool - optee_protmem_pool_init() is slightly refactored to make the patches that follow easier - Call devm_memremap() before calling tee_protmem_static_pool_alloc() Changes since V8: * Using dma_alloc_pages() instead of cma_alloc() so the direct dependency on CMA can be removed together with the patches "cma: export cma_alloc() and cma_release()" and "dma-contiguous: export dma_contiguous_default_area". The patch * Renaming the patch "tee: add tee_shm_alloc_cma_phys_mem()" to "tee: add tee_shm_alloc_dma_mem()" * Setting DMA mask for the OP-TEE TEE device based on input from the secure world instead of relying on the parent device so following patches are removed: "tee: tee_device_alloc(): copy dma_mask from parent device" and "optee: pass parent device to tee_device_alloc()". * Adding Sumit Garg's R-B to "tee: refactor params_from_user()" * In the patch "tee: implement protected DMA-heap", map the physical memory passed to tee_protmem_static_pool_alloc(). Changes since V7: * Adding "dma-buf: dma-heap: export declared functions", "cma: export cma_alloc() and cma_release()", and "dma-contiguous: export dma_contiguous_default_area" to export the symbols needed to keep the TEE subsystem as a load module. * Removing CONFIG_TEE_DMABUF_HEAP and CONFIG_TEE_CMA since they aren't needed any longer. * Addressing review comments in "optee: sync secure world ABI headers" * Better align protected memory pool initialization between the smc-abi and ffa-abi parts of the optee driver. * Removing the patch "optee: account for direction while converting parameters" Changes since V6: * Restricted memory is now known as protected memory since to use the same term as https://docs.vulkan.org/guide/latest/protected.html. Update all patches to consistently use protected memory. * In "tee: implement protected DMA-heap" add the hidden config option TEE_DMABUF_HEAP to tell if the DMABUF_HEAPS functions are available for the TEE subsystem * Adding "tee: refactor params_from_user()", broken out from the patch "tee: new ioctl to a register tee_shm from a dmabuf file descriptor" * For "tee: new ioctl to a register tee_shm from a dmabuf file descriptor": - Update commit message to mention protected memory - Remove and open code tee_shm_get_parent_shm() in param_from_user_memref() * In "tee: add tee_shm_alloc_cma_phys_mem" add the hidden config option TEE_CMA to tell if the CMA functions are available for the TEE subsystem * For "tee: tee_device_alloc(): copy dma_mask from parent device" and "optee: pass parent device to tee_device_alloc", added Reviewed-by: Sumit Garg <sumit.garg(a)kernel.org> Changes since V5: * Removing "tee: add restricted memory allocation" and "tee: add TEE_IOC_RSTMEM_FD_INFO" * Adding "tee: implement restricted DMA-heap", "tee: new ioctl to a register tee_shm from a dmabuf file descriptor", "tee: add tee_shm_alloc_cma_phys_mem()", "optee: pass parent device to tee_device_alloc()", and "tee: tee_device_alloc(): copy dma_mask from parent device" * The two TEE driver OPs "rstmem_alloc()" and "rstmem_free()" are replaced with a struct tee_rstmem_pool abstraction. * Replaced the the TEE_IOC_RSTMEM_ALLOC user space API with the DMA-heap API Changes since V4: * Adding the patch "tee: add TEE_IOC_RSTMEM_FD_INFO" needed by the GStreamer demo * Removing the dummy CPU access and mmap functions from the dma_buf_ops * Fixing a compile error in "optee: FF-A: dynamic restricted memory allocation" reported by kernel test robot <lkp(a)intel.com> Changes since V3: * Make the use_case and flags field in struct tee_shm u32's instead of u16's * Add more description for TEE_IOC_RSTMEM_ALLOC in the header file * Import namespace DMA_BUF in module tee, reported by lkp(a)intel.com * Added a note in the commit message for "optee: account for direction while converting parameters" why it's needed * Factor out dynamic restricted memory allocation from "optee: support restricted memory allocation" into two new commits "optee: FF-A: dynamic restricted memory allocation" and "optee: smc abi: dynamic restricted memory allocation" * Guard CMA usage with #ifdef CONFIG_CMA, effectively disabling dynamic restricted memory allocate if CMA isn't configured Changes since the V2 RFC: * Based on v6.12 * Replaced the flags for SVP and Trusted UID memory with a u32 field with unique id for each use case * Added dynamic allocation of restricted memory pools * Added OP-TEE ABI both with and without FF-A for dynamic restricted memory * Added support for FF-A with FFA_LEND Changes since the V1 RFC: * Based on v6.11 * Complete rewrite, replacing the restricted heap with TEE_IOC_RSTMEM_ALLOC Changes since Olivier's post [2]: * Based on Yong Wu's post [1] where much of dma-buf handling is done in the generic restricted heap * Simplifications and cleanup * New commit message for "dma-buf: heaps: add Linaro restricted dmabuf heap support" * Replaced the word "secure" with "restricted" where applicable Etienne Carriere (1): tee: new ioctl to a register tee_shm from a dmabuf file descriptor Jens Wiklander (8): optee: sync secure world ABI headers dma-buf: dma-heap: export declared functions tee: implement protected DMA-heap tee: refactor params_from_user() tee: add tee_shm_alloc_dma_mem() optee: support protected memory allocation optee: FF-A: dynamic protected memory allocation optee: smc abi: dynamic protected memory allocation drivers/dma-buf/dma-heap.c | 3 + drivers/tee/Kconfig | 5 + drivers/tee/Makefile | 1 + drivers/tee/optee/Kconfig | 5 + drivers/tee/optee/Makefile | 1 + drivers/tee/optee/core.c | 7 + drivers/tee/optee/ffa_abi.c | 146 ++++++++- drivers/tee/optee/optee_ffa.h | 27 +- drivers/tee/optee/optee_msg.h | 84 ++++- drivers/tee/optee/optee_private.h | 15 +- drivers/tee/optee/optee_smc.h | 37 ++- drivers/tee/optee/protmem.c | 335 ++++++++++++++++++++ drivers/tee/optee/smc_abi.c | 141 ++++++++- drivers/tee/tee_core.c | 157 +++++++--- drivers/tee/tee_heap.c | 500 ++++++++++++++++++++++++++++++ drivers/tee/tee_private.h | 14 + drivers/tee/tee_shm.c | 157 +++++++++- include/linux/tee_core.h | 59 ++++ include/linux/tee_drv.h | 10 + include/uapi/linux/tee.h | 31 ++ 20 files changed, 1668 insertions(+), 67 deletions(-) create mode 100644 drivers/tee/optee/protmem.c create mode 100644 drivers/tee/tee_heap.c base-commit: 038d61fd642278bab63ee8ef722c50d10ab01e8f -- 2.43.0

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Linaro-mm-sig September 2025