Linaro-mm-sig May 2026

linaro-mm-sig@lists.linaro.org

107 participants
351 discussions

by Leo Enda

Wave Rider surprised me more than I expected. The game looks simple at first, but once the speed increases and the waves become unstable, every run starts feeling intense. Unlike many endless runner games that rely only on fast movement, Wave Rider creates pressure through unpredictable water physics and constantly changing obstacle patterns. Play Wave Rider online at https://wave-rider.io The gameplay is built around survival. Your board moves forward automatically while you focus on steering through dangerous sections of water. Floating barriers, underwater mines, sharp turns, and narrow lanes appear quickly, forcing players to react within seconds. What I liked most is how the game balances smooth surfing movement with sudden moments of chaos. Sometimes the water feels calm, then everything changes when multiple obstacles appear together. Wave Rider also rewards risky decisions. Pearls are often hidden near dangerous routes, making players choose between safe movement and higher scores. I found myself taking bigger risks after every run just to see how far I could push the distance counter. The durability system adds even more tension because repeated small crashes slowly reduce your chance of surviving longer sessions. Game Controls Left Arrow / A: Move left Right Arrow / D: Move right Spacebar or Up Arrow: Jump or glide over obstacles The controls are easy to learn, but mastering the timing takes practice. Quick reactions help, but smooth movement and patience usually lead to better runs. Players who panic and change direction too aggressively often crash faster than expected. Overall, Wave Rider feels like a solid arcade experience for anyone who enjoys reaction-based gameplay. The combination of flowing water, rising speed, and nonstop danger makes every session feel fresh and competitive.

2 weeks, 6 days

[PATCH v18 00/42] DEPT(DEPendency Tracker)

by Byungchul Park

I'm happy to see that DEPT reported real problems in practice: https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… https://lore.kernel.org/all/b6e00e77-4a8c-4e05-ab79-266bf05fcc2d@igalia.com/ I’ve added documentation describing DEPT — this should help you understand what DEPT is and how it works. You can use DEPT simply by enabling CONFIG_DEPT and checking dmesg at runtime. --- Hi Linus and folks, I’ve been developing a tool to detect deadlock possibilities by tracking waits/events — rather than lock acquisition order — to cover all the synchronization mechanisms. To summarize the design rationale, starting from the problem statement, through analysis, to the solution: CURRENT STATUS -------------- Lockdep tracks lock acquisition order to identify deadlock conditions. Additionally, it tracks IRQ state changes — via {en,dis}able — to detect cases where locks are acquired unintentionally during interrupt handling. PROBLEM ------- Waits and their associated events that are never reachable can eventually lead to deadlocks. However, since Lockdep focuses solely on lock acquisition order, it has inherent limitations when handling waits and events. Moreover, by tracking only lock acquisition order, Lockdep cannot properly handle read locks or cross-event scenarios — such as wait_for_completion() and complete() — making it increasingly inadequate as a general-purpose deadlock detection tool. SOLUTION -------- Once again, waits and their associated events that are never reachable can eventually lead to deadlocks. The new solution, DEPT, focuses directly on waits and events. DEPT monitors waits and events, and reports them when any become unreachable. DEPT provides: * Correct handling of read locks. * Support for general waits and events. * Continuous operation, even after multiple reports. * Simple, intuitive annotation APIs. There are still false positives, and some are already being worked on for suppression. Especially splitting the folio class into several appropriate classes e.g. block device mapping class and regular file mapping class, is currently under active development by me and Yeoreum Yun. Anyway, these efforts will need to continue for a while, as we’ve seen with lockdep over two decades. DEPT is tagged as EXPERIMENTAL in Kconfig — meaning it’s not yet suitable for use as an automation tool. However, for those who are interested in using DEPT to analyze complex synchronization patterns and extract dependency insights, DEPT would be a great tool for the purpose. Thanks for your support and contributions to: Harry Yoo <harry.yoo(a)oracle.com> Gwan-gyeong Mun <gwan-gyeong.mun(a)intel.com> Yunseong Kim <ysk(a)kzalloc.com> Yeoreum Yun <yeoreum.yun(a)arm.com> FAQ --- Q. Is this the first attempt to solve this problem? A. No. The cross-release feature (commit b09be676e0ff2) attempted to address it — as a Lockdep extension. It was merged, but quickly reverted, because: While it uncovered valuable hidden issues, it also introduced false positives. Since these false positives mask further real problems with Lockdep — and developers strongly dislike them — the feature was rolled back. Q. Why wasn’t DEPT built as a Lockdep extension? A. Lockdep is the result of years of work by kernel developers — and is now very stable. But I chose to build DEPT separately, because: While reusing BFS(Breadth First Search) and Lockdep’s hashing is beneficial, the rest of the system must be rebuilt from scratch to align with DEPT’s wait-event model — since Lockdep was originally designed for tracking lock acquisition orders, not wait-event dependencies. Q. Do you plan to replace Lockdep entirely? A. Not at all — Lockdep still plays a vital role in validating correct lock usage. While its dependency-checking logic should eventually be superseded by DEPT, the rest of its functionality should stay. Q. Should we replace the dependency check immediately? A. Absolutely not. Lockdep’s stability is the result of years of hard work by kernel developers. Lockdep and DEPT should run side by side until DEPT matures. Q. Stronger detection often leads to more false positives — which was a major pain point when cross-release was added. Is DEPT designed to handle this? A. Yes. DEPT’s simple, generalized design enables flexible reporting — so while false positives still need fixing, they’re far less disruptive than they were under the Lockdep extension, cross-release. Q. Why not fix all false positives out-of-tree before merging? A. Since the affected subsystems span the entire kernel, like Lockdep, which has relied on annotations to avoid false positives over the last two decades, DEPT too will require the annotation efforts. Performing annotation work within the mainline will help us add annotations more appropriately and will also make DEPT a useful tool for a wider range of users more quickly. CONFIG_DEPT is marked EXPERIMENTAL, so it’s opt-in. Some users are already interested in using DEPT to analyze complex synchronization patterns and extract dependency insights. Byungchul --- Changes from v17: 1. Rebase on the mainline as of 2025 Dec 5. 2. Convert the documents' format from txt to rst. (feedbacked by Jonathan Corbet and Bagas Sanjaya) 3. Move the documents from 'Documentation/dependency' to 'Documentation/dev-tools'. (feedbakced by Jonathan Corbet) 4. Improve the documentation. (feedbacked by NeilBrown) 5. Use a common function, enter_from_user_mode(), instead of arch specific code, to notice context switch from user mode. (feedbacked by Dave Hansen, Mark Rutland, and Mark Brown) 6. Resolve the header dependency issue by using dept's internal header, instead of relocating 'struct llist_{head,node}' to another header. (feedbacked by Greg KH) 7. Improve page(or folio) usage type APIs. 8. Add rust helper for wait_for_completion(). (feedbacked by Guangbo Cui, Boqun Feng, and Danilo Krummrich) 9. Refine some commit messages. Changes from v16: 1. Rebase on v6.17. 2. Fix a false positive from rcu (by Yunseong Kim) 3. Introduce APIs to set page's usage, dept_set_page_usage() and dept_reset_page_usage() to avoid false positives. 4. Consider lock_page() as a potential wait unconditionally. 5. Consider folio_lock_killable() as a potential wait unconditionally. 6. Add support for tracking PG_writeback waits and events. 7. Fix two build errors due to the additional debug information added by dept. (by Yunseong Kim) Changes from v15: 1. Fix typo and improve comments and commit messages (feedbacked by ALOK TIWARI, Waiman Long, and kernel test robot). 2. Do not stop dept on detection of cicular dependency of recover event, allowing to keep reporting. 3. Add SK hynix to copyright. 4. Consider folio_lock() as a potential wait unconditionally. 5. Fix Kconfig dependency bug (feedbacked by kernel test rebot). 6. Do not suppress reports that involve classes even that have already involved in other reports, allowing to keep reporting. Changes from v14: 1. Rebase on the current latest, v6.15-rc6. 2. Refactor dept code. 3. With multi event sites for a single wait, even if an event forms a circular dependency, the event can be recovered by other event(or wake up) paths. Even though informing the circular dependency is worthy but it should be suppressed once informing it, if it doesn't lead an actual deadlock. So introduce APIs to annotate the relationship between event site and recover site, that are, event_site() and dept_recover_event(). 4. wait_for_completion() worked with dept map embedded in struct completion. However, it generates a few false positves since all the waits using the instance of struct completion, share the map and key. To avoid the false positves, make it not to share the map and key but each wait_for_completion() caller have its own key by default. Of course, external maps also can be used if needed. 5. Fix a bug about hardirq on/off tracing. 6. Implement basic unit test for dept. 7. Add more supports for dma fence synchronization. 8. Add emergency stop of dept e.g. on panic(). 9. Fix false positives by mmu_notifier_invalidate_*(). 10. Fix recursive call bug by DEPT_WARN_*() and DEPT_STOP(). 11. Fix trivial bugs in DEPT_WARN_*() and DEPT_STOP(). 12. Fix a bug that a spin lock, dept_pool_spin, is used in both contexts of irq disabled and enabled without irq disabled. 13. Suppress reports with classes, any of that already have been reported, even though they have different chains but being barely meaningful. 14. Print stacktrace of the wait that an event is now waking up, not only stacktrace of the event. 15. Make dept aware of lockdep_cmp_fn() that is used to avoid false positives in lockdep so that dept can also avoid them. 16. Do do_event() only if there are no ecxts have been delimited. 17. Fix a bug that was not synchronized for stage_m in struct dept_task, using a spin lock, dept_task()->stage_lock. 18. Fix a bug that dept didn't handle the case that multiple ttwus for a single waiter can be called at the same time e.i. a race issue. 19. Distinguish each kernel context from others, not only by system call but also by user oriented fault so that dept can work with more accuracy information about kernel context. That helps to avoid a few false positives. 20. Limit dept's working to x86_64 and arm64. Changes from v13: 1. Rebase on the current latest version, v6.9-rc7. 2. Add 'dept' documentation describing dept APIs. Changes from v12: 1. Refine the whole document for dept. 2. Add 'Interpret dept report' section in the document, using a deadlock report obtained in practice. Hope this version of document helps guys understand dept better. https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… Changes from v11: 1. Add 'dept' documentation describing the concept of dept. 2. Rewrite the commit messages of the following commits for using weaker lockdep annotation, for better description. fs/jbd2: Use a weaker annotation in journal handling cpu/hotplug: Use a weaker annotation in AP thread (feedbacked by Thomas Gleixner) Changes from v10: 1. Fix noinstr warning when building kernel source. 2. dept has been reporting some false positives due to the folio lock's unfairness. Reflect it and make dept work based on dept annotaions instead of just wait and wake up primitives. 3. Remove the support for PG_writeback while working on 2. I will add the support later if needed. 4. dept didn't print stacktrace for [S] if the participant of a deadlock is not lock mechanism but general wait and event. However, it made hard to interpret the report in that case. So add support to print stacktrace of the requestor who asked the event context to run - usually a waiter of the event does it just before going to wait state. 5. Give up tracking raw_local_irq_{disable,enable}() since it totally messed up dept's irq tracking. So make it work in the same way as lockdep does. I will consider it once any false positives by those are observed again. 6. Change the manual rwsem_acquire_read(->j_trans_commit_map) annotation in fs/jbd2/transaction.c to the try version so that it works as much as it exactly needs. 7. Remove unnecessary 'inline' keyword in dept.c and add '__maybe_unused' to a needed place. Changes from v9: 1. Fix a bug. SDT tracking didn't work well because of my big mistake that I should've used waiter's map to indentify its class but it had been working with waker's one. FYI, PG_locked and PG_writeback weren't affected. They still worked well. (reported by YoungJun) Changes from v8: 1. Fix build error by adding EXPORT_SYMBOL(PG_locked_map) and EXPORT_SYMBOL(PG_writeback_map) for kernel module build - appologize for that. (reported by kernel test robot) 2. Fix build error by removing header file's circular dependency that was caused by "atomic.h", "kernel.h" and "irqflags.h", which I introduced - appolgize for that. (reported by kernel test robot) Changes from v7: 1. Fix a bug that cannot track rwlock dependency properly, introduced in v7. (reported by Boqun and lockdep selftest) 2. Track wait/event of PG_{locked,writeback} more aggressively assuming that when a bit of PG_{locked,writeback} is cleared there might be waits on the bit. (reported by Linus, Hillf and syzbot) 3. Fix and clean bad style code e.i. unnecessarily introduced a randome pattern and so on. (pointed out by Linux) 4. Clean code for applying dept to wait_for_completion(). Changes from v6: 1. Tie to task scheduler code to track sleep and try_to_wake_up() assuming sleeps cause waits, try_to_wake_up()s would be the events that those are waiting for, of course with proper dept annotations, sdt_might_sleep_weak(), sdt_might_sleep_strong() and so on. For these cases, class is classified at sleep entrance rather than the synchronization initialization code. Which would extremely reduce false alarms. 2. Remove the dept associated instance in each page struct for tracking dependencies by PG_locked and PG_writeback thanks to the 1. work above. 3. Introduce CONFIG_dept_AGGRESIVE_TIMEOUT_WAIT to suppress reports that waits with timeout set are involved, for those who don't like verbose reporting. 4. Add a mechanism to refill the internal memory pools on running out so that dept could keep working as long as free memory is available in the system. 5. Re-enable tracking hashed-waitqueue wait. That's going to no longer generate false positives because class is classified at sleep entrance rather than the waitqueue initailization. 6. Refactor to make it easier to port onto each new version of the kernel. 7. Apply dept to dma fence. 8. Do trivial optimizaitions. Changes from v5: 1. Use just pr_warn_once() rather than WARN_ONCE() on the lack of internal resources because WARN_*() printing stacktrace is too much for informing the lack. (feedback from Ted, Hyeonggon) 2. Fix trivial bugs like missing initializing a struct before using it. 3. Assign a different class per task when handling onstack variables for waitqueue or the like. Which makes dept distinguish between onstack variables of different tasks so as to prevent false positives. (reported by Hyeonggon) 4. Make dept aware of even raw_local_irq_*() to prevent false positives. (reported by Hyeonggon) 5. Don't consider dependencies between the events that might be triggered within __schedule() and the waits that requires __schedule(), real ones. (reported by Hyeonggon) 6. Unstage the staged wait that has prepare_to_wait_event()'ed *and* yet to get to __schedule(), if we encounter __schedule() in-between for another sleep, which is possible if e.g. a mutex_lock() exists in 'condition' of ___wait_event(). 7. Turn on CONFIG_PROVE_LOCKING when CONFIG_DEPT is on, to rely on the hardirq and softirq entrance tracing to make dept more portable for now. Changes from v4: 1. Fix some bugs that produce false alarms. 2. Distinguish each syscall context from another *for arm64*. 3. Make it not warn it but just print it in case dept ring buffer gets exhausted. (feedback from Hyeonggon) 4. Explicitely describe "EXPERIMENTAL" and "dept might produce false positive reports" in Kconfig. (feedback from Ted) Changes from v3: 1. dept shouldn't create dependencies between different depths of a class that were indicated by *_lock_nested(). dept normally doesn't but it does once another lock class comes in. So fixed it. (feedback from Hyeonggon) 2. dept considered a wait as a real wait once getting to __schedule() even if it has been set to TASK_RUNNING by wake up sources in advance. Fixed it so that dept doesn't consider the case as a real wait. (feedback from Jan Kara) 3. Stop tracking dependencies with a map once the event associated with the map has been handled. dept will start to work with the map again, on the next sleep. Changes from v2: 1. Disable dept on bit_wait_table[] in sched/wait_bit.c reporting a lot of false positives, which is my fault. Wait/event for bit_wait_table[] should've been tagged in a higher layer for better work, which is a future work. (feedback from Jan Kara) 2. Disable dept on crypto_larval's completion to prevent a false positive. Changes from v1: 1. Fix coding style and typo. (feedback from Steven) 2. Distinguish each work context from another in workqueue. 3. Skip checking lock acquisition with nest_lock, which is about correct lock usage that should be checked by lockdep. Changes from RFC(v0): 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). (feedback from Linus and Matthew) 2. Use try version at lockdep_acquire_cpus_lock() annotation. 3. Distinguish each syscall context from another. Byungchul Park (41): dept: implement DEPT(DEPendency Tracker) dept: add single event dependency tracker APIs dept: add lock dependency tracker APIs dept: tie to lockdep and IRQ tracing dept: add proc knobs to show stats and dependency graph dept: distinguish each kernel context from another dept: distinguish each work from another dept: add a mechanism to refill the internal memory pools on running out dept: record the latest one out of consecutive waits of the same class dept: apply sdt_might_sleep_{start,end}() to wait_for_completion()/complete() dept: apply sdt_might_sleep_{start,end}() to swait dept: apply sdt_might_sleep_{start,end}() to waitqueue wait dept: apply sdt_might_sleep_{start,end}() to hashed-waitqueue wait dept: apply sdt_might_sleep_{start,end}() to dma fence dept: track timeout waits separately with a new Kconfig dept: apply timeout consideration to wait_for_completion()/complete() dept: apply timeout consideration to swait dept: apply timeout consideration to waitqueue wait dept: apply timeout consideration to hashed-waitqueue wait dept: apply timeout consideration to dma fence wait dept: make dept able to work with an external wgen dept: track PG_locked with dept dept: print staged wait's stacktrace on report locking/lockdep: prevent various lockdep assertions when lockdep_off()'ed dept: add documents for dept cpu/hotplug: use a weaker annotation in AP thread dept: assign dept map to mmu notifier invalidation synchronization dept: assign unique dept_key to each distinct dma fence caller dept: make dept aware of lockdep_set_lock_cmp_fn() annotation dept: make dept stop from working on debug_locks_off() dept: assign unique dept_key to each distinct wait_for_completion() caller completion, dept: introduce init_completion_dmap() API dept: introduce a new type of dependency tracking between multi event sites dept: add module support for struct dept_event_site and dept_event_site_dep dept: introduce event_site() to disable event tracking if it's recoverable dept: implement a basic unit test for dept dept: call dept_hardirqs_off() in local_irq_*() regardless of irq state dept: introduce APIs to set page usage and use subclasses_evt for the usage dept: track PG_writeback with dept SUNRPC: relocate struct rcu_head to the first field of struct rpc_xprt mm: percpu: increase PERCPU_DYNAMIC_SIZE_SHIFT on DEPT and large PAGE_SIZE Yunseong Kim (1): rcu/update: fix same dept key collision between various types of RCU Documentation/dev-tools/dept.rst | 778 ++++++ Documentation/dev-tools/dept_api.rst | 125 + drivers/dma-buf/dma-fence.c | 23 +- include/asm-generic/vmlinux.lds.h | 13 +- include/linux/completion.h | 124 +- include/linux/dept.h | 402 +++ include/linux/dept_ldt.h | 78 + include/linux/dept_sdt.h | 68 + include/linux/dept_unit_test.h | 67 + include/linux/dma-fence.h | 74 +- include/linux/hardirq.h | 3 + include/linux/irq-entry-common.h | 4 + include/linux/irqflags.h | 21 +- include/linux/local_lock_internal.h | 1 + include/linux/lockdep.h | 105 +- include/linux/lockdep_types.h | 3 + include/linux/mm_types.h | 4 + include/linux/mmu_notifier.h | 26 + include/linux/module.h | 5 + include/linux/mutex.h | 1 + include/linux/page-flags.h | 217 +- include/linux/pagemap.h | 37 +- include/linux/percpu-rwsem.h | 2 +- include/linux/percpu.h | 4 + include/linux/rcupdate_wait.h | 13 +- include/linux/rtmutex.h | 1 + include/linux/rwlock_types.h | 1 + include/linux/rwsem.h | 1 + include/linux/sched.h | 118 + include/linux/seqlock.h | 2 +- include/linux/spinlock_types_raw.h | 3 + include/linux/srcu.h | 2 +- include/linux/sunrpc/xprt.h | 9 +- include/linux/swait.h | 3 + include/linux/wait.h | 3 + include/linux/wait_bit.h | 3 + init/init_task.c | 2 + init/main.c | 2 + kernel/Makefile | 1 + kernel/cpu.c | 2 +- kernel/dependency/Makefile | 5 + kernel/dependency/dept.c | 3499 ++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_internal.h | 314 +++ kernel/dependency/dept_object.h | 13 + kernel/dependency/dept_proc.c | 94 + kernel/dependency/dept_unit_test.c | 173 ++ kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/locking/lockdep.c | 33 + kernel/module/main.c | 19 + kernel/rcu/rcu.h | 1 + kernel/rcu/update.c | 5 +- kernel/sched/completion.c | 62 +- kernel/sched/core.c | 9 + kernel/workqueue.c | 3 + lib/Kconfig.debug | 48 + lib/debug_locks.c | 2 + lib/locking-selftest.c | 2 + mm/filemap.c | 38 + mm/mm_init.c | 3 + mm/mmu_notifier.c | 31 +- rust/helpers/completion.c | 5 + 63 files changed, 6602 insertions(+), 121 deletions(-) create mode 100644 Documentation/dev-tools/dept.rst create mode 100644 Documentation/dev-tools/dept_api.rst create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_ldt.h create mode 100644 include/linux/dept_sdt.h create mode 100644 include/linux/dept_unit_test.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_internal.h create mode 100644 kernel/dependency/dept_object.h create mode 100644 kernel/dependency/dept_proc.c create mode 100644 kernel/dependency/dept_unit_test.c base-commit: 43dfc13ca972988e620a6edb72956981b75ab6b0 -- 2.17.1

2 weeks, 6 days

Prepare to Rage Quit (and Maybe Love It): Diving into Level Devil

by graceful.earthworm.hsos＠hidingmail.com

So, you're looking for a new game to sink your teeth into? Something challenging, maybe a little bit infuriating, and definitely memorable? Look no further than Level Devil. This deceptively simple platformer is a masterclass in trickery, constantly changing the rules and keeping you on your toes. But don't be intimidated! With a little patience (and maybe a stress ball), you can conquer its devilish design. https://leveldevilfull.com Gameplay: Expect the Unexpected At its core, Level Devil is a 2D platformer. You control a little pixelated character tasked with reaching the exit door in each level. Sounds easy, right? Wrong. The beauty (and the frustration) lies in the unpredictable nature of the environment. Platforms crumble beneath your feet, spikes appear out of nowhere, and the ground itself can vanish unexpectedly. Each level introduces new challenges, forcing you to adapt your strategy on the fly. You'll encounter moving platforms, disappearing blocks, and even gravity-defying puzzles. The real kicker? The layout of the levels often changes on each attempt, meaning memorization alone won't cut it. You need to be quick-witted and reactive. The charm of Level Devil is its lack of hand-holding. There are no tutorials, no hints, and no mercy. You're thrown straight into the deep end, forced to learn from your mistakes (and trust me, there will be plenty). That feeling of finally overcoming a particularly difficult section is incredibly rewarding. It's a game that demands your full attention and rewards persistence. Tips for Taming the Devil While Level Devil thrives on its unpredictability, here are a few tips to help you navigate its treacherous landscape: • Patience is Key: This game is designed to test your limits. Don't get discouraged by frequent deaths. Treat each attempt as a learning experience. • Observe Carefully: Before making a move, take a moment to scan the environment. Look for subtle cues that might indicate impending danger. • Embrace Failure: You will die. A lot. Embrace it as part of the learning process. Each death provides valuable insight into the level's design. • Don't Overthink It: Sometimes, the solution is simpler than you think. Avoid overcomplicating your approach. • Take Breaks: If you find yourself getting too frustrated, step away from the game for a while. Come back with a fresh perspective. • Listen to the Sound: The game’s audio cues often hint at upcoming dangers. Pay close attention! Level Devil utilizes sound design to enhance the experience (and sometimes, to cleverly mislead you!). Conclusion: A Test of Skill and Sanity Level Devil isn't for the faint of heart. It's a challenging and often frustrating experience. However, it's also incredibly rewarding. The constant surprises, the need for quick thinking, and the sheer satisfaction of overcoming its devilish design make it a truly unique and memorable game. If you're looking for a platformer that will push you to your limits and leave you feeling accomplished, then Level Devil is definitely worth a try. Just be prepared to rage quit... and then come back for more.

3 weeks, 2 days

Wordle Unlimited Game Guide for Endless Word Puzzle Fun

by thoughtless.stork.wxrl＠hidingmail.net

Introduction to Wordle Unlimited Experience Wordle Unlimited is an online word puzzle game that expands the classic word guessing concept into an endless format. Instead of waiting for a daily puzzle, players can enjoy continuous gameplay with unlimited attempts and unlimited rounds. This format makes it appealing for players who enjoy vocabulary challenges, logic thinking, and casual gaming without time restrictions. https://wordleunlimitedgame.org/ The main objective remains simple. Players try to guess a hidden five letter word within a limited number of attempts. After each guess, feedback is provided through color indicators that help narrow down the correct answer. This simple design combined with endless replay value makes Wordle Unlimited highly engaging for both beginners and experienced puzzle players. How Wordle Unlimited Gameplay Works Wordle Unlimited follows a straightforward set of rules that are easy to understand. Each round begins with a hidden word that players must discover. Players enter a five letter word as a guess, and the system responds with color coded hints. Green indicates a correct letter in the correct position. Yellow indicates a correct letter in the wrong position. Gray indicates a letter that is not part of the hidden word. These feedback signals guide players toward the correct answer step by step. Unlike traditional daily word puzzles, Wordle Unlimited allows continuous play without waiting periods. Players can restart instantly after finishing a round, making it suitable for practice, entertainment, or improving vocabulary skills. This unlimited structure also allows experimentation with different guessing strategies. Key Features of Wordle Unlimited One of the most important features of Wordle Unlimited is unlimited gameplay. Players are not restricted to a single puzzle per day, which increases engagement and learning opportunities. This feature is especially useful for users who enjoy repetitive practice or competitive improvement. Another key feature is accessibility. The game runs directly in a web browser, meaning no installation is required. It works on desktop computers, tablets, and mobile devices, making it convenient for users in different environments. Wordle Unlimited also maintains a simple interface. There are no complicated menus or distractions. The focus remains entirely on word solving. This minimal design helps players concentrate and improves the overall puzzle solving experience. Additionally, the game supports learning and vocabulary development. Players are exposed to different word patterns and letter combinations, which can help improve language skills over time. Effective Strategies for Winning Wordle Unlimited A strong strategy in Wordle Unlimited begins with choosing a good starting word. Many players select words that contain common vowels and frequently used consonants. This approach increases the chance of identifying correct letters early in the game. Another effective strategy is to avoid repeating incorrect letters. Once a letter is marked as gray, it is usually best to exclude it from future guesses. This helps narrow down possibilities more efficiently. Players also benefit from analyzing letter placement carefully. When a letter is marked yellow, it should be repositioned in the next guess. This process of elimination is essential for solving puzzles in fewer attempts. It is also helpful to think in word patterns rather than random guesses. English words often follow predictable structures, and recognizing these patterns can significantly improve success rates. Finally, patience plays an important role. Rushing guesses can lead to repeated mistakes. Taking time to evaluate feedback from each attempt leads to more accurate solutions. Benefits of Playing Wordle Unlimited Regularly Playing Wordle Unlimited regularly offers several cognitive benefits. One major advantage is vocabulary improvement. Players are exposed to a wide range of words, which helps expand language knowledge over time. Another benefit is mental exercise. Word puzzle games stimulate logical thinking, pattern recognition, and memory recall. These skills are useful in both academic and professional contexts. Wordle Unlimited also provides stress relief for many players. The simple structure and short gameplay sessions make it a relaxing activity that can be enjoyed during breaks or free time. In addition, the unlimited nature of the game allows continuous practice. This is especially beneficial for players who want to improve performance or challenge themselves with faster solving times. Social interaction is another indirect benefit. Many players enjoy sharing results or competing with friends, which adds a fun and competitive element to the experience. Why Wordle Unlimited Remains Popular The popularity of Wordle Unlimited comes from its balance of simplicity and challenge. It does not require advanced gaming skills, yet it still offers a satisfying mental challenge. This combination makes it accessible to a wide audience. The unlimited format also contributes to its popularity. Players are no longer restricted by daily limits, which means they can engage with the game whenever they want. This flexibility aligns well with modern digital habits. Another reason for its popularity is its quick gameplay loop. Each round can be completed in a short time, making it ideal for casual entertainment. Despite its simplicity, the game continues to offer new challenges with every hidden word. Conclusion on Wordle Unlimited Experience Wordle Unlimited delivers a simple yet highly engaging word puzzle experience that appeals to players of all ages. With unlimited gameplay, easy rules, and strong cognitive benefits, it stands out as an effective and enjoyable word game.

3 weeks, 5 days

Shred Some Slopes: Getting the Hang of Snow Rider 3D

by careful.earthworm.usil＠hidingmail.com

Feeling the need for speed and a bit of winter fun, even when the weather outside is frightful? Then maybe it’s time to check out Snow Rider 3D. This simple but surprisingly addictive game offers a thrill of downhill skiing and snowboarding right from your browser, no downloads required. Let’s break down how to jump in and start enjoying this surprisingly engaging title. https://snowriderfree.com/ Gameplay: Simple Controls, Endless Possibilities The core gameplay of Snow Rider 3D is deceptively straightforward. You control your character's direction using the left and right arrow keys (or A and D). Your objective? Navigate through a series of procedurally generated slopes littered with obstacles. These obstacles range from simple ramps and rails to more challenging hazards like trees, snowdrifts, and even abandoned shacks. The beauty of Snow Rider 3D lies in its physics. While simple, they feel surprisingly realistic. You'll need to anticipate turns, adjust your speed, and time your jumps to successfully navigate the terrain. A crash will reset you to the beginning of the course, so precision and patience are key. The game offers different levels, each presenting a unique challenge. Some focus on speed and long jumps, while others demand skillful maneuvering through tight spaces. As you progress, you unlock new skins and sleds, adding a touch of customization to your experience. Think of it as a casual time-killer that can quickly turn into an hour-long obsession! Tips for Mastering the Mountain: Alright, so you're ready to hit the slopes. Here are a few tips to help you improve your runs and avoid those frustrating wipeouts: Practice Makes Perfect: Don't get discouraged by early crashes. The more you play, the better you'll understand the physics and learn to anticipate the terrain. Master the Turns: Smooth, controlled turns are essential for maintaining speed and avoiding obstacles. Practice feathering the arrow keys to make subtle adjustments. Timing is Everything: When approaching jumps and ramps, pay close attention to your speed and angle. A well-timed jump can make all the difference. Don't Be Afraid to Slow Down: Sometimes, the fastest route isn't the safest. Don't be afraid to ease off the gas and navigate tricky sections with caution. Consider looking up guides for specific levels of Snow Rider 3D at websites like Snow Rider 3D if you’re really struggling. Experiment with Sleds and Skins: Different sleds may offer slight variations in handling. Try out different options to find one that suits your playstyle. Conclusion: A Fun and Accessible Winter Escape Snow Rider 3D is a surprisingly addictive and accessible game that’s perfect for a quick dose of winter fun. It's simple controls and challenging gameplay make it easy to pick up and play, while its procedural generation ensures that each run is a unique experience. So, whether you're looking for a casual time-killer or a challenging skill-based game, Snow Rider 3D is definitely worth checking out.

3 weeks, 6 days

Bake Your Way to Billions: A Look at the Addictive World of Store Management Games

by hot.meerkat.lloh＠hidingmail.net

Ever dreamed of running your own bustling enterprise, watching your profits soar, and building an empire from humble beginnings? If so, you've likely stumbled upon the fascinating and surprisingly addictive world of store management games. These titles offer a unique blend of strategy, incremental growth, and the satisfying feeling of seeing your hard work pay off. And when it comes to the purest, most delightful form of this genre, one game stands out: https://cookieclickers.io/ The Sweet Simplicity of Cookie Clicker: A Gateway to Management At its heart, Cookie Clicker is incredibly simple. You start with a single, humble cookie, and your goal is to click it to generate more cookies. These initial clicks are crucial, as they fund your first upgrades. Soon, you’ll be able to purchase "grandmas," who automatically bake cookies for you, freeing up your clicking finger. From there, the sky's the limit! You'll acquire farms, factories, mines, and even portals to other dimensions, all dedicated to the singular purpose of baking more and more cookies. What makes Cookie Clicker so captivating is its elegant progression system. Each new upgrade and building provides a tangible boost to your cookie production, creating a satisfying feedback loop. The numbers on your screen grow exponentially, transforming from humble dozens to mind-boggling septillions and beyond. It’s a masterclass in incremental design, making every new purchase feel impactful and exciting. Beyond the Click: Strategic Thinking and Exponential Growth While the initial appeal of Cookie Clicker might be the simple act of clicking, true mastery lies in strategic decision-making. As your cookie empire expands, you'll be faced with choices: Upgrade Prioritization: Should you invest in another Grandma, a new farm, or a powerful upgrade that boosts all your existing structures? Understanding the cost-benefit analysis of each option is key. Synergies: Many upgrades have synergistic effects, meaning they become more powerful when paired with specific buildings. Discovering these combinations is a delightful puzzle. Ascension and Prestige: Eventually, you’ll unlock the ability to “ascend,” resetting your game but granting you powerful "heavenly chips" that provide permanent bonuses. This meta-progression adds a whole new layer of long-term strategy, encouraging you to rethink your approach with each new playthrough. These elements elevate Cookie Clicker from a simple clicking game to a genuinely engaging management simulation. It teaches you about exponential growth, compound interest (in a fun, cookie-filled way!), and the satisfaction of building something from nothing. Tips for Aspiring Cookie Tycoons If you’re ready to dive into the sweet, sweet world of Cookie Clicker, here are a few friendly tips to get you started: Don't Be Afraid to Click! In the early game, your clicks are your most valuable resource. Keep that finger moving! Invest in Grandmas Early: They're your first step towards automation and a steady cookie income. Always Buy Upgrades: The small boosts they provide add up quickly and are often more cost-effective than new buildings in the short term. Look for Golden Cookies: These appear randomly and offer temporary, powerful buffs. Clicking them can drastically boost your production! Consider Ascending: While it seems daunting to reset your progress, the permanent bonuses you gain make future runs much faster and more efficient. The Endless Appeal of Automation Cookie Clicker, and store management games in general, tap into a fundamental human desire: the joy of creation and the satisfaction of watching systems work efficiently. There's a particular kind of quiet pleasure in setting up a well-oiled machine and observing its output multiply. So, if you're looking for a game that's easy to pick up, surprisingly deep, and immensely satisfying, give Cookie Clicker a try. You might just find yourself baking billions before you know it!

3 weeks, 6 days

Why should you buy a dachshund puppy?

by Chong Criston

1 month

[PATCH 0/5] Replace the dmabuf custom test framework with kunit

by Jason Gunthorpe

Using kunit to write tests for new work on dmabuf is coming up: https://lore.kernel.org/all/26-v1-b5cab63049c0+191af-dmabuf_map_type_jgg@nv… Replace the custom test framework with kunit to avoid maintaining two concurrent test frameworks. The conversion minimizes code changes and uses simple pattern-oriented reworks to reduce the chance of breaking any tests. Aside from adding the kunit_test_suite() boilerplate, the conversion follows a number of patterns: Test failures without cleanup. For example: if (!ptr) return -ENOMEM; Becomes: KUNIT_ASSERT_NOT_NULL(test, ptr); In kunit ASSERT longjumps out of the test. Check for error, fail and cleanup: if (err) { pr_err("msg\n"); goto cleanup; } Becomes: if (err) { KUNIT_FAIL(test, "msg"); goto cleanup; } Preserve the existing failure messages and cleanup code. Cases where the test returns err but prints no message: if (err) goto cleanup; Becomes: if (err) { KUNIT_FAIL(test, "msg"); goto cleanup; } Use KUNIT_FAIL to retain the 'cleanup on err' behavior. Overall, the conversion is straightforward. The result can be run with kunit.py: $ tools/testing/kunit/kunit.py run --build_dir build_kunit_x86_64 --arch x86_64 --kunitconfig ./drivers/dma-buf/.kunitconfig [20:37:23] Configuring KUnit Kernel ... [20:37:23] Building KUnit Kernel ... Populating config with: $ make ARCH=x86_64 O=build_kunit_x86_64 olddefconfig Building with: $ make all compile_commands.json scripts_gdb ARCH=x86_64 O=build_kunit_x86_64 --jobs=20 [20:37:29] Starting KUnit Kernel (1/1)... [20:37:29] ============================================================ Running tests with: $ qemu-system-x86_64 -nodefaults -m 1024 -kernel build_kunit_x86_64/arch/x86/boot/bzImage -append 'kunit.enable=1 console=ttyS0 kunit_shutdown=reboot' -no-reboot -nographic -accel kvm -accel hvf -accel tcg -serial stdio -bios qboot.rom [20:37:30] ================ dma-buf-resv (5 subtests) ================= [20:37:30] [PASSED] test_sanitycheck [20:37:30] ===================== test_signaling ====================== [20:37:30] [PASSED] kernel [20:37:30] [PASSED] write [20:37:30] [PASSED] read [20:37:30] [PASSED] bookkeep [20:37:30] ================= [PASSED] test_signaling ================== ... [20:37:35] Testing complete. Ran 50 tests: passed: 49, skipped: 1 [20:37:35] Elapsed time: 12.635s total, 0.001s configuring, 6.551s building, 6.017s running One test that requires two CPUs is skipped since the default VM has a single CPU and cannot run the test. All other usual ways to run kunit work as well, and all tests are placed in a module to provide more options for how they are run. AI was used to do the large scale semantic search and replaces described above, then everything was hand checked. AI also deduced the issue with test_race_signal_callback() in a couple of seconds from the kunit crash (!!), again was hand checked though I am not so familiar with this test to be fully certain this is the best answer. Jason Gunthorpe (5): dma-buf: Change st-dma-resv.c to use kunit dma-buf: Change st-dma-fence.c to use kunit dma-buf: Change st-dma-fence-unwrap.c to use kunit dma-buf: Change st-dma-fence-chain.c to use kunit dma-buf: Remove the old selftest drivers/dma-buf/.kunitconfig | 2 + drivers/dma-buf/Kconfig | 11 +- drivers/dma-buf/Makefile | 5 +- drivers/dma-buf/selftest.c | 167 --------------- drivers/dma-buf/selftest.h | 30 --- drivers/dma-buf/selftests.h | 16 -- drivers/dma-buf/st-dma-fence-chain.c | 217 +++++++++---------- drivers/dma-buf/st-dma-fence-unwrap.c | 290 +++++++++++--------------- drivers/dma-buf/st-dma-fence.c | 200 ++++++++---------- drivers/dma-buf/st-dma-resv.c | 145 +++++++------ drivers/gpu/drm/i915/Kconfig.debug | 2 +- 11 files changed, 394 insertions(+), 691 deletions(-) create mode 100644 drivers/dma-buf/.kunitconfig delete mode 100644 drivers/dma-buf/selftest.c delete mode 100644 drivers/dma-buf/selftest.h delete mode 100644 drivers/dma-buf/selftests.h base-commit: 41dae5ac5e157b0bb260f381eb3df2f4a4610205 -- 2.43.0

1 month

[PATCH 00/15] accel/qda: Qualcomm DSP Accelerator driver

by Ekansh Gupta via B4 Relay

This patch series introduces the Qualcomm DSP Accelerator (QDA) driver, a DRM-based accelerator driver for Qualcomm DSPs. The driver provides a standardized interface for offloading computational tasks to DSPs found on Qualcomm SoCs, supporting all DSP domains. The QDA driver implements the FastRPC protocol over the DRM accel subsystem. It uses the same device-tree node structure as the existing fastrpc driver in drivers/misc/. The approach for binding the QDA driver to device-tree nodes while coexisting with the fastrpc driver is an open item described below. RFC thread: https://lore.kernel.org/dri-devel/20260224-qda-firstpost-v1-0-fe46a9c1a046@… User-space staging branch ========================= https://github.com/qualcomm/fastrpc/tree/accel/staging Key Features ============ * Standard DRM accelerator interface via /dev/accel/accelN * GEM-based buffer management with DMA-BUF import/export (PRIME) * IOMMU-based memory isolation using per-process context banks * FastRPC protocol implementation for DSP communication * RPMsg transport layer for reliable message passing * Support for all DSP domains (ADSP, CDSP, SDSP, GDSP) * DRM IOCTL interface for DSP session management, buffer allocation, and remote procedure invocation Architecture ============ 1. DRM Accelerator Framework Integration The driver registers as a DRM accel device, exposing a standard /dev/accel/accelN character device node. This provides established DRM infrastructure for device management, file operations, and IOCTL dispatch. 2. Memory Management Buffers are managed as GEM objects with full PRIME support for DMA-BUF import/export. This enables seamless buffer sharing with other DRM drivers (GPU, camera, video) using standard kernel mechanisms. 3. IOMMU Context Bank Management IOMMU context banks (CBs) are represented as proper struct device instances on a custom virtual bus (qda-compute-cb). Each CB device is registered with the IOMMU subsystem and receives its own IOMMU domain, enabling per-session address space isolation. The custom bus was introduced because IOMMU context banks are synthetic constructs — not real platform devices — and to ensure CB device lifetime is strictly subordinate to the parent QDA device. See also: https://lore.kernel.org/all/245d602f-3037-4ae3-9af9-d98f37258aae@oss.qualco… 4. Memory Manager Architecture A pluggable memory manager coordinates IOMMU device assignment and buffer allocation. The current implementation uses a DMA-coherent backend with SID-prefixed DMA addresses for DSP firmware compatibility. 5. Transport Layer RPMsg communication is handled in a dedicated transport layer (qda_rpmsg.c), separate from the core DRM driver logic. 6. Code Organization The driver is organized across multiple files (~4600 lines total): * qda_drv.c: Core driver and DRM integration * qda_rpmsg.c: RPMsg transport layer * qda_cb.c: Context bank device management * qda_compute_bus.c: Custom virtual bus for CB devices * qda_gem.c: GEM object management * qda_prime.c: DMA-BUF import (PRIME) * qda_memory_manager.c: IOMMU device registry and allocation * qda_memory_dma.c: DMA-coherent allocation backend * qda_fastrpc.c: FastRPC protocol implementation * qda_ioctl.c: IOCTL dispatch 7. UAPI Design The driver exposes DRM-style IOCTLs defined in include/uapi/drm/qda_accel.h, following DRM UAPI conventions (__u32/__u64 types, C++ guard, GPL-2.0-only WITH Linux-syscall-note). Patch Series Organization ========================== Patch 01: MAINTAINERS entry Patch 02: Driver documentation (Documentation/accel/qda/) Patches 03-04: Core driver skeleton and compute bus Patch 05: iommu: Register qda-compute-cb bus with IOMMU subsystem Patches 06-07: CB device enumeration and memory manager Patch 08: QUERY IOCTL and UAPI header Patches 09-11: GEM buffer management and PRIME import Patches 12-15: FastRPC protocol (invoke, session create/release, map/unmap) Open Items =========== 1. Device-Tree Compatible String The QDA driver uses the same device-tree node structure and properties as the existing fastrpc driver in drivers/misc/. A mechanism is needed to allow the QDA driver to bind to its device node independently of the fastrpc driver. The intended coexistence model is: platforms that require the complete fastrpc feature set continue to use "qcom,fastrpc"; new platforms where a feature available only in QDA takes priority, or where QDA's current feature set is sufficient, use a QDA-specific compatible string. New feature development is directed toward QDA rather than the existing fastrpc driver. As QDA matures toward feature parity with fastrpc, platforms can adopt the QDA-specific compatible string exclusively. The options under consideration are: a) Add a new "qcom,qda" compatible string to the existing qcom,fastrpc.yaml binding, since the DT node structure and properties are identical. This avoids a separate binding file but adds a QDA-specific string to a fastrpc binding. b) Introduce a separate qcom,qda.yaml binding that references or inherits the fastrpc binding properties. Seeking guidance from DT binding maintainers on the preferred approach. 2. Privilege Level Management Currently, daemon processes and user processes have the same access level as both use the same accel device node. This needs to be addressed as daemons attach to privileged DSP protection domains and require higher privilege levels for system-level operations. Seeking guidance on the best approach: separate device nodes, capability-based checks, or DRM master/authentication mechanisms. 3. UAPI Compatibility Layer A compatibility layer is needed to facilitate migration of client applications from the existing FastRPC UAPI to the new QDA UAPI, ensuring a smooth transition for existing userspace code. Seeking guidance on the preferred implementation approach: in-kernel translation layer, userspace wrapper library, or hybrid solution. An initial evaluation of an in-kernel translation shim was performed, where legacy FastRPC device nodes (/dev/fastrpc-*) are exposed and requests are internally routed to the QDA accel driver. The goal was to keep the compatibility layer minimal, reuse existing QDA helper paths (attach, buffer allocation, mapping, etc.), and avoid duplication of GEM and buffer management logic. However, the following challenges were identified: a) Dependency on drm_file for QDA helpers QDA relies on GEM-backed allocations and per-client handle namespaces, which require a valid struct drm_file. Since GEM handles are scoped per drm_file, the compatibility layer cannot directly reuse QDA helper paths without establishing a proper drm_file context for each client. b) Lack of public API for drm_file creation Creating a drm_file directly (similar to mock_drm_getfile()-style approaches) is not feasible, as the required helpers (drm_file_alloc(), drm_file_free(), etc.) are internal to the DRM core and not exported. This prevents external drivers from safely constructing and managing drm_file instances. c) VFS-based open is not a viable solution Opening the underlying accel device (/dev/accel/accelN) from the compatibility driver via filp_open() does provide a valid drm_file, but introduces reliance on userspace-visible device paths, lack of stability in containerized or chroot environments, and no clean mapping between legacy device nodes and accel devices. d) Userspace proxy limitations (CUSE) A CUSE-based userspace proxy was evaluated. However, DMA-buf file descriptors passed by legacy applications cannot be directly reused in the CUSE daemon (file descriptors are process-specific), which breaks buffer sharing semantics. e) drm_client-based approaches do not match requirements drm_client APIs (used for fbdev emulation) rely on a shared drm_file and do not provide the per-client isolation required by FastRPC semantics. Due to the above constraints, it is currently unclear how to implement an in-kernel compatibility layer that correctly handles per-client drm_file contexts without relying on VFS paths or non-exported DRM internals. 4. Documentation Improvements Add detailed IOCTL usage examples, document DSP firmware interface requirements, and create a migration guide from the existing FastRPC driver. 5. Per-Session Memory Allocation Develop a userspace API to support memory allocation on a per-session basis, enabling session-specific memory management. 6. Audio and Sensors PD Support The current series does not handle Audio PD and Sensors PD functionalities. These specialized protection domains require additional support for real-time constraints and power management. Interface Compatibility ======================== The QDA driver uses the same device-tree node structure and child node layout (including "qcom,fastrpc-compute-cb" child nodes) as the existing fastrpc driver. The underlying FastRPC protocol and DSP firmware interface are compatible with the existing fastrpc driver, ensuring that DSP firmware and libraries continue to work without modification. References ========== Previous discussions on this migration: - https://lkml.org/lkml/2024/6/24/479 - https://lkml.org/lkml/2024/6/21/1252 Testing ======= The driver has been tested on Qualcomm platforms with: - Basic FastRPC attach/release operations - DSP process creation and initialization - Memory mapping/unmapping operations - Dynamic invocation with various buffer types - GEM buffer allocation and mmap - PRIME buffer import from other subsystems Signed-off-by: Ekansh Gupta <ekansh.gupta(a)oss.qualcomm.com> --- Ekansh Gupta (15): MAINTAINERS: Add entry for Qualcomm DSP Accelerator (QDA) driver accel/qda: Add QDA driver documentation accel/qda: Add initial QDA DRM accelerator driver accel/qda: Add compute bus for QDA context banks iommu: Add QDA compute context bank bus to iommu_buses accel/qda: Create compute context bank devices on QDA compute bus accel/qda: Add memory manager for CB devices accel/qda: Add QUERY IOCTL and QDA UAPI header accel/qda: Add DMA-backed GEM objects and memory manager integration accel/qda: Add GEM_CREATE and GEM_MMAP_OFFSET IOCTLs accel/qda: Add PRIME DMA-BUF import support accel/qda: Add FastRPC invocation support accel/qda: Add DSP process creation and release accel/qda: Add remote memory mapping to DSP address space accel/qda: Add remote memory unmap from DSP address space Documentation/accel/index.rst | 1 + Documentation/accel/qda/index.rst | 13 + Documentation/accel/qda/qda.rst | 146 +++++ MAINTAINERS | 9 + drivers/accel/Kconfig | 1 + drivers/accel/Makefile | 2 + drivers/accel/qda/Kconfig | 34 + drivers/accel/qda/Makefile | 19 + drivers/accel/qda/qda_cb.c | 146 +++++ drivers/accel/qda/qda_cb.h | 32 + drivers/accel/qda/qda_compute_bus.c | 68 ++ drivers/accel/qda/qda_drv.c | 192 ++++++ drivers/accel/qda/qda_drv.h | 91 +++ drivers/accel/qda/qda_fastrpc.c | 1058 ++++++++++++++++++++++++++++++++ drivers/accel/qda/qda_fastrpc.h | 390 ++++++++++++ drivers/accel/qda/qda_gem.c | 177 ++++++ drivers/accel/qda/qda_gem.h | 62 ++ drivers/accel/qda/qda_ioctl.c | 296 +++++++++ drivers/accel/qda/qda_ioctl.h | 19 + drivers/accel/qda/qda_memory_dma.c | 110 ++++ drivers/accel/qda/qda_memory_dma.h | 17 + drivers/accel/qda/qda_memory_manager.c | 380 ++++++++++++ drivers/accel/qda/qda_memory_manager.h | 75 +++ drivers/accel/qda/qda_prime.c | 184 ++++++ drivers/accel/qda/qda_prime.h | 18 + drivers/accel/qda/qda_rpmsg.c | 248 ++++++++ drivers/accel/qda/qda_rpmsg.h | 30 + drivers/iommu/iommu.c | 4 + include/linux/qda_compute_bus.h | 32 + include/uapi/drm/qda_accel.h | 229 +++++++ 30 files changed, 4083 insertions(+) --- base-commit: 80dd246accce631c328ea43294e53b2b2dd2aa32 change-id: 20260519-qda-series-78c2bf0ed78b Best regards, -- Ekansh Gupta <ekansh.gupta(a)oss.qualcomm.com>

1 month, 2 weeks

[PATCH v2 0/9] vfio/pci: Add mmap() for DMABUFs

by Matt Evans

Hi all, This series is based on previous RFCs/discussions: Tech topic: https://lore.kernel.org/linux-iommu/20250918214425.2677057-1-amastro@fb.com/ RFCv1: https://lore.kernel.org/all/20260226202211.929005-1-mattev@meta.com/ RFCv2: https://lore.kernel.org/kvm/20260312184613.3710705-1-mattev@meta.com/ The background/rationale is covered in more detail in the RFC cover letters. The TL;DR is: The goal is to enable userspace driver designs that use VFIO to export DMABUFs representing subsets of PCI device BARs, and "vend" those buffers from a primary process to other subordinate processes by fd. These processes then mmap() the buffers and their access to the device is isolated to the exported ranges. This is an improvement on sharing the VFIO device fd to subordinate processes, which would allow unfettered access. This is achieved by enabling mmap() of vfio-pci DMABUFs, passed by fd to subordinate processes. Second, a new ioctl()-based revocation mechanism is added to allow the primary process to forcibly revoke access to previously-shared BAR spans, even if the subordinate processes haven't cleanly exited. (The related topic of safe delegation of iommufd control to the subordinate processes is not addressed here, and is follow-up work.) As well as isolation and revocation, another advantage to accessing a BAR through a VMA backed by a DMABUF is that it's straightforward to mmap() the buffer with access attributes, such as write-combining. Feedback from the RFCs requested that, instead of creating DMABUF-specific vm_ops and .fault paths, to go the whole way and migrate the existing VFIO PCI BAR mmap() to be backed by a DMABUF too, resulting in a common vm_ops and fault handler for mmap()s of both the VFIO device and explicitly-exported DMABUFs. This will help future iommufd emulation of VFIO Type1 peer-to-peer, making it easier to get a DMABUF for a VFIO BAR as a DMA target. mmap() conversion to use DMABUF underneath has been done for vfio-pci, but not sub-drivers: nvgrace-gpu's mmap() override path is unchanged; I kept this out of scope for now not least because I don't have a thorough test setup for this system. I would prefer to help the nvgrace-gpu maintainers enable BAR mmap() DMABUFs themselves. Notes on patches ================ PCI/P2PDMA: Add CONFIG_PCI_P2PDMA_CORE Later in the series, vfio-pci's mmap() is going to depend on pcim_p2pdma_provider() which depended on CONFIG_PCI_P2PDMA, which in turn depended on ZONE_DEVICE (which isn't available on 32-bit and some archs, because they lack MEMORY_HOTPLUG and friends). VFIO does _not_ require actual P2P to be present for basic mmap() functionality, only for the optional CONFIG_DMA_SHARED_BUFFER feature. This splits P2PDMA into a CONFIG_PCI_P2PDMA_CORE (which currently contains pcim_p2pdma_provider()) and an optional CONFIG_PCI_P2PDMA (which depends on ZONE_DEVICE etc., and provides P2P functionality). vfio/pci: Add a helper to look up PFNs for DMABUFs vfio/pci: Add a helper to create a DMABUF for a BAR-map VMA The first is for a DMABUF VMA fault handler to determine arbitrary-sized PFNs from ranges in DMABUF. Secondly, refactor DMABUF export for use by the existing export feature and add a new helper that creates a DMABUF corresponding to a VFIO BAR mmap() request. vfio/pci: Convert BAR mmap() to use a DMABUF The vfio-pci core mmap() creates a DMABUF with the helper, and the vm_ops fault handler uses the other helper to resolve the fault. Because this depends on DMABUF structs/code, CONFIG_VFIO_PCI_CORE needs to depend on CONFIG_DMA_SHARED_BUFFER. The CONFIG_VFIO_PCI_DMABUF still conditionally enables the export support code. NOTE: The user mmap()s a device fd, but the resulting VMA's vm_file becomes that of the DMABUF which takes ownership of the device and puts it on release. This maintains the existing behaviour of a VMA keeping the VFIO device open. BAR zapping then happens via the existing vfio_pci_dma_buf_move() path, which now needs to unmap PTEs in the DMABUF's address_space. vfio/pci: Provide a user-facing name for BAR mappings There was a request for decent debug naming in /proc/<pid>/maps etc. comparable to the existing VFIO names: since the VMAs are DMABUFs, they have a "dmabuf:" prefix and can't be 100% identical to before. This is a user-visible change, but this patch at least now gives us extra info on the BDF & BAR being mapped. vfio/pci: Clean up BAR zap and revocation In general (see NOTE!) the vfio_pci_zap_bars() is now obsolete, since it unmaps PTEs in the VFIO device address_space which is now unused. This consolidates all calls (e.g. around reset) with the neighbouring vfio_pci_dma_buf_move()s into new functions, to revoke-zap/unrevoke. !!! NOTE: the nvgrace-gpu driver continues to use its own private vm_ops, fault handler, etc. for its special memregions, and these DO still add PTEs to the VFIO device address_space. So, a temporary flag, vdev->bar_needs_zap, maintains the old behaviour for this use. At least this patch's consolidation makes it easy to remove the remaining zap when this need goes away; a FIXME reminds that this can be removed when nvgrace-gpu is converted. vfio/pci: Support mmap() of a VFIO DMABUF Adds mmap() for a DMABUF fd exported from vfio-pci. It was a goal to keep the VFIO device fd lifetime behaviour unchanged with respect to the DMABUFs. An application can close all device fds, and this will revoke/clean up all DMABUFs; no mappings or other access can be performed now. When enabling mmap() of the DMABUFs, this means access through the VMA is also revoked. This complicates the fault handler because whilst the DMABUF exists, it has no guarantee that the corresponding VFIO device is still alive. Adds synchronisation ensuring the vdev is available before vdev->memory_lock is touched; this holds the device registration so that even if the buffer has been cleaned up, vdev hasn't been freed and so the lock can be safely taken. (I decided against the alternative of preventing cleanup by holding the VFIO device open if any DMABUFs exist, because it's both a change of behaviour and less clean overall.) I've added a chonky comment in place, happy to clarify more if you have ideas. This commit makes VFIO_PCI_CORE depend on PCI_P2PDMA_CORE (commit 1) to bring in (only) the P2PDMA provider code. vfio/pci: Permanently revoke a DMABUF on request By weight, this is mostly a rename of revoked to an enum, status. There are now 3 states for a buffer, usable and revoked temporary/permanent. A new VFIO device ioctl is added, VFIO_DEVICE_PCI_DMABUF_REVOKE, which passes a DMABUF (exported from that device) and permanently revokes it. Thus a userspace driver can guarantee any downstream consumers of a shared fd are prevented from accessing a BAR range, and that range can be reused. The code doing revocation in vfio_pci_dma_buf_move() is moved, unchanged, to a common function for use by _move() and the new ioctl path. Q: I can't think of a good reason to temporarily revoke/unrevoke buffers from userspace, so didn't add a 'flags' field to the ioctl struct. Easy to add if people think it's worthwhile for future use. vfio/pci: Add mmap() attributes to DMABUF feature Adds a new VFIO feature, VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR. After a DMABUF is exported, this feature ioctl() isused to set a memory attribute that will be used by future mmap()s of the DMABUF fd (i.e. it does nothing for any existing maps). The default is UC, and via the feature one can specify CPU access as WC. The attribute is an enum/scalar rather than bitmap/cumulative. The attributes follow a "try-fail" model where a client can request an attribute and either succeed or fail with ENOTSUPP if it's unknown; if future attributes are platform-specific then their support can be probed. (Since it's just UC/WC for now, there is no reservation or numeric structure to the namespace yet, but we could support system/arch-specific values in future by carving out base + arch-specific + IMPDEF ranges.) Testing ======= (The [RFC ONLY] userspace test program, for QEMU edu-plus, has been dropped from the series, but can be found in the GitHub branch below. It at least illustrates the export, map, revoke, attribute, and close semantics interoperate.) This code has been tested in mapping DMABUFs of single/multiple ranges, aliasing mmap()s, aliasing ranges across DMABUFs, vm_pgoff > 0, revocation, shutdown/cleanup scenarios, and hugepage mappings seem to work correctly. I've lightly tested WC mappings also (by observing resulting PTEs as having the correct attributes...). No regressions observed on the VFIO selftests, or on our internal vfio-pci applications. End === This is based on VFIO next (e.g. at b9285405c5f6). These commits are on GitHub for easier browsing, along with "[RFC ONLY] selftests: vfio: Add standalone vfio_dmabuf_mmap_test": https://github.com/metamev/linux/compare/b9285405c5f6...metamev:linux:dev/m… Thanks for reading, Matt ================================================================================ Change log: v2: - Rebase on VFIO next, picking up Alex's vfio_pci_dma_buf_move()/vfio_pci_dma_buf_cleanup() fixes, and dropping "vfio/pci: Fix vfio_pci_dma_buf_cleanup() double-put" - Added "PCI/P2PDMA: Add CONFIG_PCI_P2PDMA_CORE" so that the newly-added vfio-pci hard dependency on the P2PDMA provider instead pulls in the _CORE variant and not the full-fat CONFIG_PCI_P2PDMA. This means that the core of vfio-pci does not need ZONE_DEVICE, but if it's available then enabling P2PDMA in turn enables DMABUF export. Fixes basic VFIO operation on 32b or other platforms without ZONE_DEVICE. - Fixed comment inaccuracy in vfio_pci_dma_buf_revoke() and cleaned up vdev validity test. - vfio_pci_dma_buf_find_pfn(): use PAGE_ALIGN(), better span variable naming, OVF check - Made vm_pgoffs use consistent (keeping the resource index at the top and masking where offset is used). For BAR mmap, use new vma_pgoff_adjust to create the DMABUF with the exact mmap()ed span instead of from the start of the BAR with an invisible portion before the mapping. - Added VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR to set memory attributes, instead of using the export `flags` field. - vfio_pci_ioctl_reset: Moved vfio_pci_zap_revoke_bars() (effectively, vfio_pci_dma_buf_move()) back after D0 transition. Note, if a BAR zap is needed, it's done in this function so now happens after this D0 transition with the _move; it was done before it at the time of the memory_lock taking. - Minimised vfio_pci_dma_buf_mmap() (removed redundant span check), added READ_ONCE for memattr - Misc fixes: comment in DMABUF name generation, removed superfluous READ_ONCE from faulthandler v1: https://lore.kernel.org/kvm/20260416131815.2729131-1-mattev@meta.com/ - Cleanup of the common DMABUF-aware VMA vm_ops fault handler and export code. - Fixed a lot of races, particularly faults racing with DMABUF cleanup (if the VFIO device fds close, for example). - Added nicer human-readable names for VFIO mmap() VMAs RFCv2: Respin based on the feedback/suggestions: https://lore.kernel.org/kvm/20260312184613.3710705-1-mattev@meta.com/ - Transform the existing VFIO BAR mmap path to also use DMABUFs behind the scenes, and then simply share that code for explicitly-mapped DMABUFs. Jason wanted to go that direction to enable iommufd VFIO type 1 emulation to pick up a DMABUF for an IO mapping. - Revoke buffers using a VFIO device fd ioctl RFCv1: https://lore.kernel.org/all/20260226202211.929005-1-mattev@meta.com/ Matt Evans (9): PCI/P2PDMA: Add CONFIG_PCI_P2PDMA_CORE vfio/pci: Add a helper to look up PFNs for DMABUFs vfio/pci: Add a helper to create a DMABUF for a BAR-map VMA vfio/pci: Convert BAR mmap() to use a DMABUF vfio/pci: Provide a user-facing name for BAR mappings vfio/pci: Clean up BAR zap and revocation vfio/pci: Support mmap() of a VFIO DMABUF vfio/pci: Permanently revoke a DMABUF on request vfio/pci: Add mmap() attributes to DMABUF feature drivers/pci/Kconfig | 10 +- drivers/pci/Makefile | 2 +- drivers/pci/p2pdma.c | 16 + drivers/vfio/pci/Kconfig | 4 +- drivers/vfio/pci/Makefile | 3 +- drivers/vfio/pci/nvgrace-gpu/main.c | 5 + drivers/vfio/pci/vfio_pci_config.c | 30 +- drivers/vfio/pci/vfio_pci_core.c | 225 +++++++++--- drivers/vfio/pci/vfio_pci_dmabuf.c | 548 ++++++++++++++++++++++++---- drivers/vfio/pci/vfio_pci_priv.h | 57 ++- include/linux/pci-p2pdma.h | 24 +- include/linux/pci.h | 2 +- include/linux/vfio_pci_core.h | 1 + include/uapi/linux/vfio.h | 57 +++ 14 files changed, 815 insertions(+), 169 deletions(-) -- 2.47.3

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Linaro-mm-sig May 2026