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Philip Yang 61c057105d drm/amdgpu: Resync UALink ring wptr after reboot
When one side of UALink nodes reboots, its ring wptr resets to 0 while
the peer keeps a stale value. Read the remote wptr and adopt it as the
local wptr and rptr to resync, before the first message is sent. Either
side can notice first, so do this both when setting up the connection
and when receiving the HELLO from the peer.

On the sdma path, read the wptr in a fence callback because the IB buffer
holding the result is recycled once the fence signals, so reading it
after dma_fence_wait_timeout() is too late. The lsdma path copies
synchronously, so it reads the wptr directly.

Take peer->lock in the callers (amdgpu_ualink_remote_interrupt and
amdgpu_ualink_remote_shootdown) instead of in amdgpu_ualink_send_command,
so the ring->ready check and the send are atomic against a concurrent
ring reset.

Move the rptr refresh and ring-full check out of amdgpu_ualink_send_command()
into amdgpu_ualink_ring_check_space(), so it runs under the caller's
peer->lock before the job is allocated.

On a failed NPA-REQ send, reset the connection like the NPA-RSP timeout path
already does, so the next attempt resyncs the ring wptr.

On connection reset, amdgpu_ualink_reset_peer_rings() only clears
ring->ready, so the writeback address is re-registered on the next send.

v10:
  - Fix the resync missed on the receiving side: after a reboot the peer
    may send HELLO before we set up the connection, so resync the ring
    wptr in amdgpu_ualink_process_hello_msg() too.

v9:
  - Fix the unnecessary connection reset after an app exits: the peer is
    idle here but still busy handling NPA revokes on the remote, so the
    HELLO reset a healthy connection. Only send it if the wptr changed.
  - Resync both rings together under peer->lock, read both remote wptr
    before updating either so a failed read changes nothing.

v8:
  - Fix regression with concurrent import ioctls: do the idle check and
    ring reset in amdgpu_ualink_setup_connection() under conn_state->lock,
    and return -EAGAIN for IN_PROGRESS/PENDING first.
  - Reset the peer rings only, the imp/exp xarray cleanup is not needed to
    resync wptr.

v7:
  - With v6 reboot one node of vPOD test passed on minirack.
  - Use the per-remote imported and exported handle lists for the idle
    check instead of walking the xarrays.
  - Rename amdgpu_ualink_resync_peer_rings() to
    amdgpu_ualink_reset_peer_rings(), it only clears ring->ready.

v6:
  - Check idleness per remote accelerator instead of globally, and reset
    the stale connection at the import ioctl so the peer re-runs the
    HELLO handshake after a reboot.

v5:
  - Resync the ring pointers at the import ioctl when the connection is
    completely idle (no exported or imported BOs), so the first command
    from a new application after a remote reboot/reset succeeds.
  - Put the sdma wptr read fence callback on the stack instead of
    allocating it; it is cancelled on timeout so it never outlives the
    call.

v4:
  - Cancel the sdma fence callback on the wait timeout/failure path so it
    cannot write into the caller's stack after the function returns, and
    free the callback state in one place.

v3:
  - Resync both rings at connection setup instead of on the send path.
  - Set the writeback rptr too, the stale value disagrees with the
    resynced wptr until the remote FW writes it back.

v2:
  - Match the FW change: resync wptr only on the first send or after a
    timeout, instead of checking the remote periodically.

Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Mukul Joshi <mukul.joshi@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
History 2026-09-23 13:03:13 -04:00
arch x86 fixes: 2026-09-20 09:49:10 -07:00
block block: save page offset gaps in cloned bio 2026-09-01 08:42:34 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto This push fixes a memory allocation overrun in crypto acomp. 2026-08-28 09:28:40 -07:00
Documentation Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
drivers drm/amdgpu: Resync UALink ring wptr after reboot 2026-09-23 13:03:13 -04:00
fs Timer race fixes: 2026-09-20 09:41:00 -07:00
include Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
init Bootconfig fixes for v7.3-rc3 2026-09-13 09:16:36 -07:00
io_uring io_uring-7.3-20260911 2026-09-11 12:36:13 -07:00
ipc mm.git review status for master..mm-nonmm-stable 2026-08-23 08:07:11 -07:00
kernel Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
lib 14 hotfixes. 10 are cc:stable. 11 are for MM. 2026-09-14 08:59:09 -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 memblock: fix for regions display in debugfs and MAINTAINERS update 2026-09-14 09:36:43 -07:00
net net: qrtr: resend HELLO on MHI resume 2026-09-20 11:21:10 -07:00
rust Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
samples rust: samples: add missing newlines in rust_print_main 2026-09-01 02:20:22 +02:00
scripts x86 fixes: 2026-09-20 09:49:10 -07:00
security selinux/stable-7.3 PR 20260919 2026-09-20 06:50:31 -07:00
sound Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
tools x86 fixes: 2026-09-20 09:49:10 -07:00
usr usr: Correct a spelling by changing a letter 2026-08-05 14:51:58 +02:00
virt Arm: 2026-08-25 11:48:04 -07:00
.clang-format drm/bridge: rename drm_for_each_bridge_in_chain_scoped() to drm_for_each_bridge_in_chain() 2026-07-14 17:55:51 +02:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-09-07 10:01:33 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap 14 hotfixes. 10 are cc:stable. 11 are for MM. 2026-09-14 08:59:09 -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 Driver core fixes for 7.3-rc2 2026-09-05 11:59:05 -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 Linux 7.3-rc4 2026-09-22 18:35:06 +10:00
Makefile Linux 7.3-rc4 2026-09-20 13:48:15 -07:00
README README: remove out of place emdashes 2026-07-15 10:51:29 -06:00

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