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Keith Busch 102c8b26b5 PCI: Allow all bus devices to use the same slot
A PCIe hotplug slot applies to the entire secondary bus. Thus, pciehp only
allocates a single hotplug_slot for the bridge to that bus. The existing
PCI slot, though, would only match to functions on device 0, meaning any
devices beyond that, e.g., ARI functions, are not matched to any slot even
though they share it. A slot reset will break all the missing devices
because the handling skips them.

For example, ARI devices with more than 8 functions fail because their
state is not properly handled, nor is the attached driver notified of the
reset. In the best case, the device will appear unresponsive to the driver,
resulting in unexpected errors. A worse possibility may panic the kernel if
in-flight transactions trigger hardware reported errors like this real
observation:

  vfio-pci 0000:01:00.0: resetting
  vfio-pci 0000:01:00.0: reset done
  {1}[Hardware Error]:  Error 1, type: fatal
  {1}[Hardware Error]:   section_type: PCIe error
  {1}[Hardware Error]:   port_type: 0, PCIe end point
  {1}[Hardware Error]:   version: 0.2
  {1}[Hardware Error]:   command: 0x0140, status: 0x0010
  {1}[Hardware Error]:   device_id: 0000:01:01.0
  {1}[Hardware Error]:   slot: 0
  {1}[Hardware Error]:   secondary_bus: 0x00
  {1}[Hardware Error]:   vendor_id: 0x1d9b, device_id: 0x0207
  {1}[Hardware Error]:   class_code: 020000
  {1}[Hardware Error]:   bridge: secondary_status: 0x0000, control: 0x0000
  {1}[Hardware Error]:   aer_cor_status: 0x00008000, aer_cor_mask: 0x00002000
  {1}[Hardware Error]:   aer_uncor_status: 0x00010000, aer_uncor_mask: 0x00100000
  {1}[Hardware Error]:   aer_uncor_severity: 0x006f6030
  {1}[Hardware Error]:   TLP Header: 0a412800 00192080 60000004 00000004
  GHES: Fatal hardware error but panic disabled
  Kernel panic - not syncing: GHES: Fatal hardware error

Allow a slot to be created to claim all devices on a bus, not just a
matching device. This is done by introducing a sentinel value, named
PCI_SLOT_ALL_DEVICES, which then has the PCI slot match to any device on
the bus. This fixes slot resets for pciehp.

Since 0xff already has special meaning, the chosen value for this new
feature is 0xfe. This will not clash with any actual slot number since they
are limited to 5 bits.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://patch.msgid.link/20260217160836.2709885-3-kbusch@meta.com
History 2026-03-09 15:39:07 -05:00
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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