From 2bc6b218717b9d08f466f88209251d54bc09b207 Mon Sep 17 00:00:00 2001 From: Fuad Tabba Date: Tue, 22 Sep 2026 19:14:30 +0100 Subject: arm64/boot: Disable trapping of PMZR_EL0 writes to EL2 __init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2. PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a write from EL0 reaches the trap and takes the host down without a panic message. Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9 bits. Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9") Cc: stable@vger.kernel.org Signed-off-by: Fuad Tabba Reviewed-by: Anshuman Khandual Reviewed-by: Oliver Upton Signed-off-by: Will Deacon --- Documentation/process/coding-assistants.rst | 96 +++++++++++++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 Documentation/process/coding-assistants.rst (limited to 'Documentation/process/coding-assistants.rst') diff --git a/Documentation/process/coding-assistants.rst b/Documentation/process/coding-assistants.rst new file mode 100644 index 000000000..051f0d819 --- /dev/null +++ b/Documentation/process/coding-assistants.rst @@ -0,0 +1,96 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _coding_assistants: + +AI Coding Assistants +++++++++++++++++++++ + +This document provides guidance for AI tools and developers using AI +assistance when contributing to the Linux kernel. + +AI tools helping with Linux kernel development should follow the standard +kernel development process: + +* Documentation/process/development-process.rst +* Documentation/process/coding-style.rst +* Documentation/process/submitting-patches.rst + +For guidelines on content generated by AI coding assistants see: + +* Documentation/process/generated-content.rst + +Licensing and Legal Requirements +================================ + +All contributions must comply with the kernel's licensing requirements: + +* All code must be compatible with GPL-2.0-only +* Use appropriate SPDX license identifiers +* See Documentation/process/license-rules.rst for details + +Signed-off-by and Developer Certificate of Origin +================================================= + +AI agents MUST NOT add Signed-off-by tags. Only humans can legally +certify the Developer Certificate of Origin (DCO). The human submitter +is responsible for: + +* Reviewing all AI-generated code +* Ensuring compliance with licensing requirements +* Adding their own Signed-off-by tag to certify the DCO +* Taking full responsibility for the contribution + +Attribution +=========== + +When AI tools contribute to kernel development, proper attribution +helps track the evolving role of AI in the development process. +Contributions should include an Assisted-by tag in the following format:: + + Assisted-by: LLM [TOOL1] [TOOL2] + +* ``[TOOL1] [TOOL2]`` are optional specialized analysis tools used + (e.g., coccinelle, sparse, smatch, clang-tidy) + +Basic development tools (git, gcc, make, editors) should not be listed. + +Example:: + + Assisted-by: LLM coccinelle sparse + +Procedure for finding and fixing bugs +===================================== + +When an AI assistant is used to find and fix bugs, it **MUST** follow at least +these steps: + +1. Before starting, read the whole process documentation listed above, as well + as any other document mentioned in the request. Do not rely on isolated + parts found by keyword search. +2. Note the commit ID and Locate a bug as instructed. +3. For any bug found that is not trivial, verify that it looks real by + attempting to create a reproducer to demonstrate it. Lacking it may cause + the report to be ignored, as many unverified bug reports sent to maintainers + happen to be invalid. Stop here if it finally looks wrong. +4. Write a fix for the bug. This part is not optional: except in a few very + rare cases, an AI assistant able to find a bug is able to fix it. Note that + fixes written in the same session as used to find the bug will generally + lead to better and more accurate fixes as the LLM's reasoning context + remains present. +5. Build and verify that the fix works either using the reproducer or by + re-running a complete analysis; drop any fix that doesn't work and try + another one. The fix must not add build warnings and must pass the + checkpatch.pl checks (see submitting-patches.rst). +6. Commit the working fix with a detailed message describing the problem, the + solution and a Fixes tag. Do not add a Signed-off-by tag, and add an + Assisted-by tag, as described above. +7. Identify the maintainers and lists using scripts/get_maintainer.pl. + Documentation/process/security-bugs.rst shows how to do that. +8. Indicate what could not be done. If the fix could not be built or tested, or + if no reproducer could be produced, say so explicitly: maintainers currently + waste too much time analyzing unverified reports and untested fixes. +9. Read Documentation/process/threat-model.rst to determine whether the bug is + a vulnerability or a regular bug, and leave the result to the reporter for + review (the assistant must never send anything itself). Regular bugs are + submitted as described in Documentation/process/submitting-patches.rst, + vulnerabilities as described in Documentation/process/security-bugs.rst. -- cgit v1.3.1