Linaro-mm-sig January 2026

linaro-mm-sig@lists.linaro.org

44 participants
37 discussions

by Christian König

Hi everyone, dma_fences have ever lived under the tyranny dictated by the module lifetime of their issuer, leading to crashes should anybody still holding a reference to a dma_fence when the module of the issuer was unloaded. The basic problem is that when buffer are shared between drivers dma_fence objects can leak into external drivers and stay there even after they are signaled. The dma_resv object for example only lazy releases dma_fences. So what happens is that when the module who originally created the dma_fence unloads the dma_fence_ops function table becomes unavailable as well and so any attempt to release the fence crashes the system. Previously various approaches have been discussed, including changing the locking semantics of the dma_fence callbacks (by me) as well as using the drm scheduler as intermediate layer (by Sima) to disconnect dma_fences from their actual users, but none of them are actually solving all problems. Tvrtko did some really nice prerequisite work by protecting the returned strings of the dma_fence_ops by RCU. This way dma_fence creators where able to just wait for an RCU grace period after fence signaling before they could be save to free those data structures. Now this patch set here goes a step further and protects the whole dma_fence_ops structure by RCU, so that after the fence signals the pointer to the dma_fence_ops is set to NULL when there is no wait nor release callback given. All functionality which use the dma_fence_ops reference are put inside an RCU critical section, except for the deprecated issuer specific wait and of course the optional release callback. Additional to the RCU changes the lock protecting the dma_fence state previously had to be allocated external. This set here now changes the functionality to make that external lock optional and allows dma_fences to use an inline lock and be self contained. v4: Rebases the whole set on upstream changes, especially the cleanup from Philip in patch "drm/amdgpu: independence for the amdkfd_fence!". Adding two patches which brings the DMA-fence self tests up to date. The first selftest changes removes the mock_wait and so actually starts testing the default behavior instead of some hacky implementation in the test. This one got upstreamed independent of this set. The second drops the mock_fence as well and tests the new RCU and inline spinlock functionality. v5: Rebase on top of drm-misc-next instead of drm-tip, leave out all driver changes for now since those should go through the driver specific paths anyway. Address a few more review comments, especially some rebase mess and typos. And finally fix one more bug found by AMDs CI system. Especially the first patch still needs a Reviewed-by, apart from that I think I've addressed all review comments and problems. Please review and comment, Christian.

6 months, 3 weeks

[PATCH v2 0/2] dma-buf: system_heap: account for system heap allocation in memcg

by Eric Chanudet

Capture dmabuf system heap allocations in memcg following prior conversations[1][2]. Disable this behavior by default unless configured by "dma_heap.mem_accounting" module parameter. [1] https://lore.kernel.org/dri-devel/Z-5GZ3kJDbhgVBPG@phenom.ffwll.local/ [2] https://lore.kernel.org/all/CABdmKX2_UOENujpW0dXe0Z0x+4V3onfGDmHf1DMOXfDha6… Changes in v2: - Add a module parameter to enable dma-buf cgroup accounting, disabled by default. - Split system_heap logic in its own commit. - Link to v1: https://lore.kernel.org/lkml/20251211193106.755485-2-echanude@redhat.com/ Signed-off-by: Eric Chanudet <echanude(a)redhat.com> --- Eric Chanudet (2): dma-buf: heaps: add parameter to account allocations using cgroup dma-buf: system_heap: account for system heap allocation in memcg drivers/dma-buf/dma-heap.c | 5 +++++ drivers/dma-buf/heaps/system_heap.c | 9 +++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) --- base-commit: b71e635feefc852405b14620a7fc58c4c80c0f73 change-id: 20260102-dmabuf-heap-system-memcg-c86a381d663a Best regards, -- Eric Chanudet <echanude(a)redhat.com>

6 months, 3 weeks

[PATCH 0/5] New DRM accel driver for Texas Instruments' C7x DSPs

by Tomeu Vizoso

This series adds a new DRM/Accel driver that supports the C7x DSPs inside some Texas Instruments SoCs such as the J722S. These can be used as accelerators for various workloads, including machine learning inference. This driver controls the power state of the hardware via remoteproc and communicates with the firmware running on the DSP via rpmsg_virtio. The kernel driver itself allocates buffers, manages contexts, and submits jobs to the DSP firmware. Buffers are mapped by the DSP itself using its MMU, providing memory isolation among different clients. The source code for the firmware running on the DSP is available at: https://gitlab.freedesktop.org/tomeu/thames_firmware/. Everything else is done in userspace, as a Gallium driver (also called thames) that is part of the Mesa3D project: https://docs.mesa3d.org/teflon.html If there is more than one core that advertises the same rpmsg_virtio service name, the driver will load balance jobs between them with drm-gpu-scheduler. Userspace portion of the driver: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39298 Signed-off-by: Tomeu Vizoso <tomeu(a)tomeuvizoso.net> --- Tomeu Vizoso (5): arm64: dts: ti: k3-j722s-ti-ipc-firmware: Add memory pool for DSP i/o buffers accel/thames: Add driver for the C7x DSPs in TI SoCs accel/thames: Add IOCTLs for BO creation and mapping accel/thames: Add IOCTL for job submission accel/thames: Add IOCTL for memory synchronization Documentation/accel/thames/index.rst | 28 ++ MAINTAINERS | 9 + .../boot/dts/ti/k3-j722s-ti-ipc-firmware.dtsi | 11 +- drivers/accel/Kconfig | 1 + drivers/accel/Makefile | 3 +- drivers/accel/thames/Kconfig | 26 ++ drivers/accel/thames/Makefile | 11 + drivers/accel/thames/thames_core.c | 161 +++++++ drivers/accel/thames/thames_core.h | 53 +++ drivers/accel/thames/thames_device.c | 93 +++++ drivers/accel/thames/thames_device.h | 46 ++ drivers/accel/thames/thames_drv.c | 180 ++++++++ drivers/accel/thames/thames_drv.h | 21 + drivers/accel/thames/thames_gem.c | 407 ++++++++++++++++++ drivers/accel/thames/thames_gem.h | 45 ++ drivers/accel/thames/thames_ipc.h | 204 +++++++++ drivers/accel/thames/thames_job.c | 463 +++++++++++++++++++++ drivers/accel/thames/thames_job.h | 51 +++ drivers/accel/thames/thames_rpmsg.c | 276 ++++++++++++ drivers/accel/thames/thames_rpmsg.h | 27 ++ 20 files changed, 2113 insertions(+), 3 deletions(-) --- base-commit: 27927a79b3c6aebd18f38507a8160294243763dc change-id: 20260113-thames-334127a2d91d Best regards, -- Tomeu Vizoso <tomeu(a)tomeuvizoso.net>

6 months, 3 weeks

[PATCH 0/4] dma-buf: add revoke mechanism to invalidate shared buffers

by Leon Romanovsky

This series implements a dma-buf “revoke” mechanism: to allow a dma-buf exporter to explicitly invalidate (“kill”) a shared buffer after it has been distributed to importers, so that further CPU and device access is prevented and importers reliably observe failure. Today, dma-buf effectively provides “if you have the fd, you can keep using the memory indefinitely.” That assumption breaks down when an exporter must reclaim, reset, evict, or otherwise retire backing memory after it has been shared. Concrete cases include GPU reset and recovery where old allocations become unsafe to access, memory eviction/overcommit where backing storage must be withdrawn, and security or isolation situations where continued access must be prevented. While drivers can sometimes approximate this with exporter-specific fencing and policy, there is no core dma-buf state transition that communicates “this buffer is no longer valid; fail access” across all access paths. The change in this series is to introduce a core “revoked” state on the dma-buf object and a corresponding exporter-triggered revoke operation. Once a dma-buf is revoked, new access paths are blocked so that attempts to DMA-map, vmap, or mmap the buffer fail in a consistent way. In addition, the series aims to invalidate existing access as much as the kernel allows: device mappings are torn down where possible so devices and IOMMUs cannot continue DMA. The semantics are intentionally simple: revoke is a one-way, permanent transition for the lifetime of that dma-buf instance. From a compatibility perspective, users that never invoke revoke are unaffected, and exporters that adopt it gain a core-supported enforcement mechanism rather than relying on ad hoc driver behavior. The intent is to keep the interface minimal and avoid imposing policy; the series provides the mechanism to terminate access, with policy remaining in the exporter and higher-level components. BTW, see this megathread [1] for additional context. Ironically, it was posted exactly one year ago. [1] https://lore.kernel.org/all/20250107142719.179636-2-yilun.xu@linux.intel.co… Thanks Cc: linux-rdma(a)vger.kernel.org Cc: linux-kernel(a)vger.kernel.org Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org Cc: kvm(a)vger.kernel.org Cc: iommu(a)lists.linux.dev To: Jason Gunthorpe <jgg(a)ziepe.ca> To: Leon Romanovsky <leon(a)kernel.org> To: Sumit Semwal <sumit.semwal(a)linaro.org> To: Christian König <christian.koenig(a)amd.com> To: Alex Williamson <alex(a)shazbot.org> To: Kevin Tian <kevin.tian(a)intel.com> To: Joerg Roedel <joro(a)8bytes.org> To: Will Deacon <will(a)kernel.org> To: Robin Murphy <robin.murphy(a)arm.com> Signed-off-by: Leon Romanovsky <leonro(a)nvidia.com> --- Leon Romanovsky (4): dma-buf: Introduce revoke semantics vfio: Use dma-buf revoke semantics iommufd: Require DMABUF revoke semantics iommufd/selftest: Reuse dma-buf revoke semantics drivers/dma-buf/dma-buf.c | 36 ++++++++++++++++++++++++++++++++---- drivers/iommu/iommufd/pages.c | 2 +- drivers/iommu/iommufd/selftest.c | 12 ++++-------- drivers/vfio/pci/vfio_pci_dmabuf.c | 27 ++++++--------------------- include/linux/dma-buf.h | 31 +++++++++++++++++++++++++++++++ 5 files changed, 74 insertions(+), 34 deletions(-) --- base-commit: 9ace4753a5202b02191d54e9fdf7f9e3d02b85eb change-id: 20251221-dmabuf-revoke-b90ef16e4236 Best regards, -- Leon Romanovsky <leonro(a)nvidia.com>

6 months, 4 weeks

[RFC v2 01/11] file: add callback for pre-mapping dmabuf

by asml.silence＠gmail.com

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

7 months

[PATCH] dma-buf: system_heap: account for system heap allocation in memcg

by Eric Chanudet

The system dma-buf heap lets userspace allocate buffers from the page allocator. However, these allocations are not accounted for in memcg, allowing processes to escape limits that may be configured. Pass the __GFP_ACCOUNT for our allocations to account them into memcg. Userspace components using the system heap can be constrained with, e.g: systemd-run --user --scope -p MemoryMax=10M ... Signed-off-by: Eric Chanudet <echanude(a)redhat.com> --- drivers/dma-buf/heaps/system_heap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index 4c782fe33fd4..c91fcdff4b77 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -38,10 +38,10 @@ struct dma_heap_attachment { bool mapped; }; -#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO) +#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_ACCOUNT) #define HIGH_ORDER_GFP (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \ | __GFP_NORETRY) & ~__GFP_RECLAIM) \ - | __GFP_COMP) + | __GFP_COMP | __GFP_ACCOUNT) static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP}; /* * The selection of the orders used for allocation (1MB, 64K, 4K) is designed -- 2.52.0

7 months

[RFC v2 10/11] io_uring/rsrc: add dmabuf-backed buffer registeration

by asml.silence＠gmail.com

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

7 months

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Linaro-mm-sig January 2026