Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst
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Unlike chan->direction , struct dma_device .directions field is a
bitfield. Turn chan->direction into a bitfield to make it compatible
with struct dma_device .directions .
Fixes: 7e01511443c3 ("dmaengine: xilinx_dma: Set dma_device directions")
Signed-off-by: Marek Vasut <marex@nabladev.com>
Link: https://patch.msgid.link/20260316221728.160139-1-marex@nabladev.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Both rz_dmac_disable_hw() and rz_dmac_irq_handle_channel() update the
CHCTRL register. To avoid concurrency issues when configuring
functionalities exposed by this registers, take the virtual channel lock.
All other CHCTRL updates were already protected by the same lock.
Previously, rz_dmac_disable_hw() disabled and re-enabled local IRQs, before
accessing CHCTRL registers but this does not ensure race-free access.
Remove the local IRQ disable/enable code as well.
Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: stable@vger.kernel.org
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://patch.msgid.link/20260316133252.240348-3-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
The driver lists (ld_free, ld_queue) are used in
rz_dmac_free_chan_resources(), rz_dmac_terminate_all(),
rz_dmac_issue_pending(), and rz_dmac_irq_handler_thread(), all under
the virtual channel lock. Take the same lock in rz_dmac_prep_slave_sg()
and rz_dmac_prep_dma_memcpy() as well to avoid concurrency issues, since
these functions also check whether the lists are empty and update or
remove list entries.
Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: stable@vger.kernel.org
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://patch.msgid.link/20260316133252.240348-2-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
At the end of this function, d is the traversal cursor of flist, but the
code completes found instead. This can lead to issues such as NULL pointer
dereferences, double completion, or descriptor leaks.
Fix this by completing d instead of found in the final
list_for_each_entry_safe() loop.
Fixes: aa8d18becc0c ("dmaengine: idxd: add callback support for iaa crypto")
Signed-off-by: Tuo Li <islituo@gmail.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260106032428.162445-1-islituo@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
devm_regmap_init_mmio returns an ERR_PTR() upon error, not NULL.
Fix the error check and also fix the error message. Use the error code
from ERR_PTR() instead of the wrong value in ret.
Fixes: 17ce252266c7 ("dmaengine: xilinx: xdma: Add xilinx xdma driver")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20251014061309.283468-1-alexander.stein@ew.tq-group.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Others have submitted this issue (https://lore.kernel.org/dmaengine/
20240722030405.3385-1-zhengdongxiong@gxmicro.cn/),
but it has not been fixed yet. Therefore, more supplementary information
is provided here.
As mentioned in the "PCS-CCS-CB-TCB" Producer-Consumer Synchronization of
"DesignWare Cores PCI Express Controller Databook, version 6.00a":
1. The Consumer CYCLE_STATE (CCS) bit in the register only needs to be
initialized once; the value will update automatically to be
~CYCLE_BIT (CB) in the next chunk.
2. The Consumer CYCLE_BIT bit in the register is loaded from the LL
element and tested against CCS. When CB = CCS, the data transfer is
executed. Otherwise not.
The current logic sets customer (HDMA) CS and CB bits to 1 in each chunk
while setting the producer (software) CB of odd chunks to 0 and even
chunks to 1 in the linked list. This is leading to a mismatch between
the producer CB and consumer CS bits.
This issue can be reproduced by setting the transmission data size to
exceed one chunk. By the way, in the EDMA using the same "PCS-CCS-CB-TCB"
mechanism, the CS bit is only initialized once and this issue was not
found. Refer to
drivers/dma/dw-edma/dw-edma-v0-core.c:dw_edma_v0_core_start.
So fix this issue by initializing the CYCLE_STATE and CYCLE_BIT bits
only once.
Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
Signed-off-by: LUO Haowen <luo-hw@foxmail.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/tencent_CB11AA9F3920C1911AF7477A9BD8EFE0AD05@qq.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
During the device remove process, the device is reset, causing the
configuration registers to go back to their default state, which is
zero. As the driver is checking if the event log support was enabled
before deallocating, it will fail if a reset happened before.
Do not check if the support was enabled, the check for 'idxd->evl'
being valid (only allocated if the HW capability is available) is
enough.
Fixes: 244da66cda35 ("dmaengine: idxd: setup event log configuration")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-10-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
It can happen that when the cdev .release() is called, the driver
already called ida_destroy(). Move ida_free() to the _del() path.
We see with DEBUG_KOBJECT_RELEASE enabled and forcing an early PCI
unbind.
Fixes: 04922b7445a1 ("dmaengine: idxd: fix cdev setup and free device lifetime issues")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-9-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
idxd_wq_disable_cleanup() which is called from the reset path for a
workqueue, sets the wq type to NONE, which for other parts of the
driver mean that the wq is empty (all its resources were released).
Only set the wq type to NONE after its resources are released.
Fixes: da32b28c95a7 ("dmaengine: idxd: cleanup workqueue config after disabling")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-8-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
The workqueue associated with an DSA/IAA device is not released when
the object is freed.
Fixes: 47c16ac27d4c ("dmaengine: idxd: fix idxd conf_dev 'struct device' lifetime")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-7-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
When the dmaengine "core" asks the driver to synchronize, send a Drain
operation to the device workqueue, which will wait for the already
submitted operations to finish.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-6-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
When used as a dmaengine, the DMA "core" might ask the driver to
terminate all pending requests, when that happens, flush all pending
descriptors.
In this context, flush means removing the requests from the pending
lists, so even if they are completed after, the user is not notified.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-5-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
When a Function Level Reset (FLR) happens, terminate the pending
descriptors that were issued by in-kernel users and disable the
interrupts associated with those. They will be re-enabled after FLR
finishes.
idxd_wq_flush_desc() is declared on idxd.h because it's going to be
used in by the DMA backend in a future patch.
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-4-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
In the case that the first Function Level Reset (FLR) concludes
correctly, but in the second FLR the scratch area for the saved
configuration cannot be allocated, it's possible for a invalid memory
access to happen.
Always set the deallocated scratch area to NULL after FLR completes.
Fixes: 98d187a98903 ("dmaengine: idxd: Enable Function Level Reset (FLR) for halt")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-3-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
If reporting errors to the event log is not supported by the hardware,
and an error that causes Function Level Reset (FLR) is received, the
driver will try to restore the event log even if it was not allocated.
Also, only try to free the event log if it was properly allocated.
Fixes: 6078a315aec1 ("dmaengine: idxd: Add idxd_device_config_save() and idxd_device_config_restore() helpers")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-2-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Move the check for IDXD_FLAG_CONFIGURABLE and the locking to "inside"
idxd_device_config(), as this is common to all callers, and the one
that wasn't holding the lock was an error (that was causing the
lockdep warning).
Suggested-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-1-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>