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Linus Torvalds d0ee290071 Arm:
- Restore CONFIG_PKVM_DISABLE_STAGE2_ON_PANIC to its former glory by
   making sure the config symbol is correctly spelled out in the code
 
 - Don't reset the AArch32 view of the PMU counters to zero when the
   guest is writing to them
 
 - Fix an assorted collection of memory leaks in the newly added tracing
   code
 
 - Fix the capping of ZCR_EL2 which could be used in an unsanitised way
   by an L2 guest
 
 x86:
 
 - Include the kernel's linux/mman.h in KVM selftests to ensure MADV_COLLAPSE
   is defined, as older libc versions may not provide it.
 
 - Include execinfo.h if and only if KVM selftests are building against glibc,
   and provide a test_dump_stack() for non-glibc builds.
 
 - Silence an annoying RCU splat on (even non-KVM-related) panics.  The splat
   is technically legit, but in practice not an issue.  To have a race, you
   would need to unload the KVM modules at exactly the time a panic happens;
   and speaking of incredibly rare races, taking the locks risks introducing
   a deadlock if the module unload code took the lock on a CPU that has been
   halted.  Which seems possibly more likely than the RCU grace period issue,
   so just shut it up.  This code used to be in KVM but is now outside it;
   but the x86 maintainers haven't picked it up, so here we are.
 
 - Rate-limit global clock updates once again (but without delayed work), as
   KVM was subtly relying on the old rate-limiting for NPT correction to guard
   against "update storms" when running without a master clock on systems with
   overcommitted CPUs.
 
 - Fix a brown paper bag goof where KVM checked if ERAPS is "dirty" instead of
   marking it dirty when emulating INVPCID.
 
 - Flush the TLB when transitioning from xAVIC => x2AVIC to ensure the CPU TLB
   doesn't contain AVIC-tagged entries for the APIC base GPA.
 
 - The top 10 commits fix buffer overflow (and potential TOC/TOU) flaws in the
   page state change protocol for encrypted VMs.  AI models find it quite
   easily given it was reported three times, but aren't as good at writing
   a comprehensive fix.  There's more to clean up in the area, which will
   come in 7.2.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
 "arm64:

   - Restore CONFIG_PKVM_DISABLE_STAGE2_ON_PANIC to its former glory by
     making sure the config symbol is correctly spelled out in the code

   - Don't reset the AArch32 view of the PMU counters to zero when the
     guest is writing to them

   - Fix an assorted collection of memory leaks in the newly added
     tracing code

   - Fix the capping of ZCR_EL2 which could be used in an unsanitised
     way by an L2 guest

  x86:

   - Include the kernel's linux/mman.h in KVM selftests to ensure
     MADV_COLLAPSE is defined, as older libc versions may not provide
     it.

   - Include execinfo.h if and only if KVM selftests are building
     against glibc, and provide a test_dump_stack() for non-glibc
     builds.

   - Silence an annoying RCU splat on (even non-KVM-related) panics.

     The splat is technically legit, but in practice not an issue. To
     have a race, you would need to unload the KVM modules at exactly
     the time a panic happens; and speaking of incredibly rare races,
     taking the locks risks introducing a deadlock if the module unload
     code took the lock on a CPU that has been halted. Which seems
     possibly more likely than the RCU grace period issue, so just shut
     it up. This code used to be in KVM but is now outside it; but the
     x86 maintainers haven't picked it up, so here we are.

   - Rate-limit global clock updates once again (but without delayed
     work), as KVM was subtly relying on the old rate-limiting for NPT
     correction to guard against "update storms" when running without a
     master clock on systems with overcommitted CPUs.

   - Fix a brown paper bag goof where KVM checked if ERAPS is "dirty"
     instead of marking it dirty when emulating INVPCID.

   - Flush the TLB when transitioning from xAVIC => x2AVIC to ensure the
     CPU TLB doesn't contain AVIC-tagged entries for the APIC base GPA.

   - The top 10 commits fix buffer overflow (and potential TOC/TOU)
     flaws in the page state change protocol for encrypted VMs. AI
     models find it quite easily given it was reported three times, but
     aren't as good at writing a comprehensive fix. There's more to
     clean up in the area, which will come in 7.2"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (22 commits)
  KVM: SEV: Use READ_ONCE() when reading entries/indices from PSC buffer
  KVM: SEV: Check PSC request indices against the actual size of the buffer
  KVM: SEV: Don't explicitly pass PSC buffer to snp_begin_psc()
  KVM: SEV: WARN if KVM attempts to setup scratch area with min_len==0
  KVM: SEV: Compute the correct max length of the in-GHCB scratch area
  KVM: SEV: Use the size of the PSC header as the minimum size for PSC requests
  KVM: SEV: Ignore Port I/O requests of length '0'
  KVM: SEV: Reject MMIO requests larger than 8 bytes with GHCB v2+
  KVM: SEV: Ignore MMIO requests of length '0'
  KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use
  KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor
  KVM: arm64: Fix memory leak in hyp_trace_unload()
  KVM: arm64: Fix rollback in hyp_trace_buffer_share_hyp()
  KVM: arm64: Fix meta-page unsharing in pKVM hyp tracing
  KVM: arm64: PMU: Preserve AArch32 counter low bits
  KVM: SVM: Flush the current TLB when transitioning from xAVIC => x2AVIC
  KVM: x86: Fix ERAPS RAP clear on INVPCID single-context invalidation
  KVM: arm64: Fix CONFIG_PKVM_DISABLE_STAGE2_ON_PANIC
  KVM: selftests: Guard execinfo.h inclusion for non-glibc builds
  KVM: x86: Rate-limit global clock updates on vCPU load
  ...
2026-05-29 13:47:55 -07:00
arch Merge commit 'kvm-psc-for-7.1' into HEAD 2026-05-29 20:25:59 +02:00
block block-7.1-20260529 2026-05-29 10:41:07 -07:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto crypto/krb5, rxrpc: Fix lack of pre-decrypt/pre-verify length checks 2026-05-20 16:36:45 -07:00
Documentation Including fixes from netfilter. 2026-05-28 13:13:48 -07:00
drivers IOMMU Fixes for Linux v7.1-rc5 2026-05-29 09:25:58 -07:00
fs nfsd-7.1 fixes: 2026-05-26 13:49:13 -07:00
include IOMMU Fixes for Linux v7.1-rc5 2026-05-29 09:25:58 -07:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260529 2026-05-29 10:36:57 -07:00
ipc ipc: limit next_id allocation to the valid ID range 2026-05-21 19:06:11 -07:00
kernel 13 hotfixes. 9 are for MM. 9 are cc:stable and the remaining 4 address 2026-05-26 08:23:19 -07:00
lib IOMMU Fixes for Linux v7.1-rc5 2026-05-29 09:25:58 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm 13 hotfixes. 9 are for MM. 9 are cc:stable and the remaining 4 address 2026-05-26 08:23:19 -07:00
net Including fixes from netfilter. 2026-05-28 13:13:48 -07:00
rust Rust fixes for v7.1 2026-05-09 11:24:02 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts Second round of Kbuild fixes for 7.1 2026-05-19 09:43:24 -07:00
security security/keys: fix missed RCU read section on lookup 2026-05-28 11:45:41 -07:00
sound ASoC: Fixes for v7.1 2026-05-28 13:48:04 +02:00
tools Arm: 2026-05-29 13:47:55 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM: Reject wrapped offset in kvm_reset_dirty_gfn() 2026-05-12 22:16:16 +02:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap 13 hotfixes. 9 are for MM. 9 are cc:stable and the remaining 4 address 2026-05-26 08:23:19 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS IOMMU Fixes for Linux v7.1-rc5 2026-05-29 09:25:58 -07:00
Makefile Linux 7.1-rc5 2026-05-24 13:48:06 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

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