Linaro-mm-sig May 2026

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341 discussions

[PATCH v3 00/10] Add dmabuf read/write via io_uring

by Pavel Begunkov

The patch set allows to register a dmabuf to an io_uring instance for a specified file and use it with io_uring read / write requests. The infrastructure is not tied to io_uring and there could be more users in the future. A similar idea was attempted some years ago by Keith [1], from where I borrowed a good number of changes, and later was brough up by Tushar and Vishal from Intel. It's an opt-in feature for files, and they need to implement a new file operation to use it. Only NVMe block devices are supported in this series. The user API is built on top of io_uring's "registered buffers", where a dmabuf is registered in a special way, but after it can be used as any other "registered buffer" with IORING_OP_{READ,WRITE}_FIXED requests. It's created via a new file operation and the resulted map is then passed through the I/O stack in a new iterator type. There is some additional infrastructure to bind it all, which also counts requests using a dmabuf map and managing lifetimes, which is used to implement map invalidation. It was tested for GPU <-> NVMe transfers. Also, as it maintains a long-term dma mapping, it helps with the IOMMU cost. The numbers below are for udmabuf reads previously run by Anuj for different IOMMU modes: - STRICT: before = 570 KIOPS, after = 5.01 MIOPS - LAZY: before = 1.93 MIOPS, after = 5.01 MIOPS - PASSTHROUGH: before = 5.01 MIOPS, after = 5.01 MIOPS There are some liburing tests that can serve as an example: git: https://github.com/isilence/liburing.git rw-dmabuf-tests-v3 url: https://github.com/isilence/liburing/tree/rw-dmabuf-tests-v3 [1] https://lore.kernel.org/io-uring/20220805162444.3985535-1-kbusch@fb.com/ v3: - Rework io_uring registration - Move token/map infrastructure code out of blk-mq - Simplify callbacks: remove a separate blk-mq table, which was mostly just forwarding calls (to nvme). - Don't skip dma sync depending on request direction - Fix a couple of hangs - Rename s/dma/dmabuf/ - Other small changes v2: - Don't pass raw dma addresses, wrap it into a driver specific object - Split into two objects: token and map - Implement move_notify Pavel Begunkov (10): file: add callback for creating long-term dmabuf maps iov_iter: add iterator type for dmabuf maps block: move bvec init into __bio_clone block: introduce dma map backed bio type lib: add dmabuf token infrastructure block: forward create_dmabuf_token to drivers nvme-pci: implement dma_token backed requests io_uring/rsrc: introduce buf registration structure io_uring/rsrc: extend buffer update io_uring/rsrc: add dmabuf backed registered buffers block/bio.c | 28 +++- block/blk-merge.c | 14 ++ block/blk.h | 3 +- block/fops.c | 16 ++ drivers/nvme/host/pci.c | 282 ++++++++++++++++++++++++++++++++ include/linux/bio.h | 19 ++- include/linux/blk-mq.h | 9 + include/linux/blk_types.h | 8 +- include/linux/fs.h | 2 + include/linux/io_dmabuf_token.h | 92 +++++++++++ include/linux/io_uring_types.h | 5 + include/linux/uio.h | 11 ++ include/uapi/linux/io_uring.h | 31 +++- io_uring/io_uring.c | 3 +- io_uring/rsrc.c | 266 +++++++++++++++++++++++++----- io_uring/rsrc.h | 30 +++- io_uring/rw.c | 4 +- lib/Kconfig | 4 + lib/Makefile | 2 + lib/io_dmabuf_token.c | 272 ++++++++++++++++++++++++++++++ lib/iov_iter.c | 29 +++- 21 files changed, 1071 insertions(+), 59 deletions(-) create mode 100644 include/linux/io_dmabuf_token.h create mode 100644 lib/io_dmabuf_token.c -- 2.53.0

6 days, 4 hours

[PATCH v2 0/2] arm64: tegra: Enable DMA Support on Tegra194 QSPI

by Aaron Kling via B4 Relay

The reason for this is to properly support the spi nor chip on the Jetson Xavier NX module. Prior to this, it would time out on all transfers and sometimes even trigger a cbb fault, locking up the entire unit. With this, reading and writing to the flash memory works as expected. This also fixes the tegra210-quad spi driver to properly use the dma memory space instead of the spi controllers. Without this, enabling dma on the controllers results in mmu faults. The driver change has only been tested on tegra210 / p3450 and tegra194 / p3518 as that is the only available test platforms. Tegra234 and Tegra241 should also be verified. I have p3766 for tegra234, but the qspi flash memory is firewalled by mb1 on all publicly available bootloaders, and no other spi devices are part of the devkit. --- Changes in v2: - Drop bindings patches - Add patch to use dma memory space instead of the spi controllers when dma is enabled. - Drop iommu properties from final patch - Link to v1: https://lore.kernel.org/r/20260515-tegra194-qspi-iommu-v1-0-57dfb63cd3d6@gm… --- Aaron Kling (2): spi: tegra210-quad: Allocate DMA memory for DMA engine arm64: tegra: Enable DMA Support on Tegra194 QSPI arch/arm64/boot/dts/nvidia/tegra194.dtsi | 4 ++++ drivers/spi/spi-tegra210-quad.c | 29 ++++++++++++++++++----------- 2 files changed, 22 insertions(+), 11 deletions(-) --- base-commit: c1ecb239fa3456529a32255359fc78b69eb9d847 change-id: 20260515-tegra194-qspi-iommu-e4e4644d5fdf Best regards, -- Aaron Kling <webgeek1234(a)gmail.com>

6 days, 5 hours

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by ludolftom64＠gmail.com

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6 days, 13 hours

UncertainRouteCanvas

by wernerkatherine77＠proton.me

Thermal Logic: Why Gambling Ended Up at the Heart of the German Resort Economy Thermal resorts in the 18th and 19th centuries http://auslaendische-online-casinos.de/ needed a way to keep wealthy visitors entertained past dinner. Concerts helped. Theater helped more. But nothing extended the stay — and the spending — quite like a well-appointed room where money could change hands in a socially acceptable setting. Baden-Baden understood this before most. The Kurhaus became a model not because it was unique but because it made the interdependence visible. A guest who came for the waters stayed for the tables, spent on the hotel, bought things in the shops, and left having funded an entire local economy for several days. The logic was circular and deliberately so. Civic planners in spa towns across what would become Germany replicated it, which is why the origins of casinos in Germany are not found in any single invention but in a distributed experiment conducted across dozens of small resort towns competing for the same aristocratic clientele throughout the 1800s. Bad Homburg refined the roulette wheel. Wiesbaden attracted the Russian literary crowd. Aachen positioned itself for the Belgian and French market. Each town adapted the model to its geography and its visitors, and the result was a casino culture embedded in regional identity rather than sitting apart from it. Prussia's 1868 ban interrupted that trajectory sharply. The decades that followed pushed gambling into legal ambiguity across German territories, and the post-war reconstruction of the industry happened unevenly — shaped more by which states had surviving spa infrastructure than by any coherent national policy. That patchwork is still visible today in the distribution of licensed land-based establishments, clustered around the same historic resort towns that invented the format in the first place. The digital era forced a reckoning with this geography. Online platforms do not have a location in any meaningful sense, which made the old state-by-state regulatory model collapse under its own inconsistencies. The 2021 Glücksspielstaatsvertrag addressed this by creating a unified federal framework and, critically, establishing the conditions under which providers could obtain a casino Germany EU license — a mechanism bringing domestic law into functional alignment with the internal market principles Brussels had been pressing for years. The treaty imposed strict behavioral constraints: mandatory deposit limits, real-time transaction monitoring, advertising watersheds, and a hard prohibition on certain product categories that had flourished in the unregulated online space. For operators already holding licenses in Malta or Gibraltar, the German market became accessible in theory and expensive in practice. Compliance infrastructure, local tax obligations, and the administrative requirements of the new framework made entry calculations difficult for anyone below a certain scale. Consolidation followed, as it tends to. The broader European picture remains deliberately fragmented. France runs its online market through a state-backed monopoly logic. The Netherlands introduced licensing in 2021 under its own Remote Gambling Act, with a different set of consumer protection priorities. Sweden liberalized in 2019 and has spent the years since managing the gap between projected and actual outcomes in problem gambling rates. Germany sits somewhere in this spectrum — more open than its pre-2021 self, more restrictive than the offshore destinations its residents had been using freely for years before the law caught up.

1 week

Re: DEPT (the dependency tracker) as AI review prompt?

by Yunseong Kim

Hi Harry, On 5/23/26 16:34, Harry Yoo wrote: > > > On 5/23/26 11:00 PM, Yunseong Kim wrote: >> I've previously experimented with running DEPT alongside syzkaller fuzzing, >> and many hung tasks missed by lockdep are caught by DEPT, but the resulting >> high volume of reports makes it easy for issues to get lost in the massive >> log output. Sorting through that output manually is a huge bottleneck, so >> leveraging a well-crafted AI prompt to triage the warnings and filter out >> the false positives would be incredibly valuable. > > I mean both 1) detection of deadlock issues AND 2) false positive elimination with AI. I completely agree. Implanting DEPT's model into an AI review prompt is a great idea. As you suggested, the patterns we develop for the AI could provide valuable feedback to enhance DEPT's itself. > If the review prompt is only used to eliminate DEPT's false positives, I think that would be quite hard to get broad use. > > Someone would have to build out-of-tree DEPT, collect the reports, and then feed those back into the AI. I don't think building that kind of pipeline would actually work well in practice. I also have a huge dept report of DEPT reports, and manually reviewing all of them is makes me sigh. The constant kernel rebuilds required for lockup testing every time are also quite expensive. Thanks for the summary! Best Regards, Yunseong

1 week

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by lenarichmond49＠gmail.com

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1 week

How to Hire a Hacker to remove unwanted information & files from all search engines linked on the internet

by lenarichmond49＠gmail.com

1 week, 1 day

How to Hire a Hacker to remove unwanted information & files from all search engines linked on the internet

by lenarichmond49＠gmail.com

1 week, 1 day

How to Hire a Hacker to remove unwanted information & files from all search engines linked on the internet

by lenarichmond49＠gmail.com

1 week, 1 day

[PATCH v5 0/2] dma-buf: heaps: system: add an option to allocate explicitly shared/decrypted memory

by Jiri Pirko

From: Jiri Pirko <jiri(a)nvidia.com> Confidential computing (CoCo) VMs/guests, such as AMD SEV and Intel TDX, run with private/encrypted memory which creates a challenge for devices that do not support DMA to it (no TDISP support). For kernel-only DMA operations, swiotlb bounce buffering provides a transparent solution by copying data through shared memory. However, the only way to get this memory into userspace is via the DMA API's dma_alloc_pages()/dma_mmap_pages() type interfaces which limits the use of the memory to a single DMA device, and is incompatible with pin_user_pages(). These limitations are particularly problematic for the RDMA subsystem which makes heavy use of pin_user_pages() and expects flexible memory usage between many different DMA devices. This patch series enables userspace to explicitly request shared (decrypted) memory allocations from new dma-buf system_cc_shared heap. Userspace can mmap this memory and pass the dma-buf fd to other existing importers such as RDMA or DRM devices to access the memory. The DMA API is improved to allow the dma heap exporter to DMA map the shared memory to each importing device. Based on dma-mapping-for-next e7442a68cd1ee797b585f045d348781e9c0dde0d Jiri Pirko (2): dma-mapping: introduce DMA_ATTR_CC_SHARED for shared memory dma-buf: heaps: system: add system_cc_shared heap for explicitly shared memory drivers/dma-buf/heaps/system_heap.c | 103 ++++++++++++++++++++++++++-- include/linux/dma-mapping.h | 10 +++ include/trace/events/dma.h | 3 +- kernel/dma/direct.h | 14 +++- kernel/dma/mapping.c | 13 +++- 5 files changed, 132 insertions(+), 11 deletions(-) -- 2.51.1

1 week, 1 day

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Linaro-mm-sig May 2026