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Lukas Wunner 58130e7ce6 PCI/ERR: Ensure error recoverability at all times 
commit a2f1e22390 upstream.

When the PCI core gained power management support in 2002, it introduced
pci_save_state() and pci_restore_state() helpers to restore Config Space
after a D3hot or D3cold transition, which implies a Soft or Fundamental
Reset (PCIe r7.0 sec 5.8):

  https://git.kernel.org/tglx/history/c/a5287abe398b

In 2006, EEH and AER were introduced to recover from errors by performing
a reset.  Because errors can occur at any time, drivers began calling
pci_save_state() on probe to ensure recoverability.

In 2009, recoverability was foiled by commit c82f63e411 ("PCI: check
saved state before restore"):  It amended pci_restore_state() to bail out
if the "state_saved" flag has been cleared.  The flag is cleared by
pci_restore_state() itself, hence a saved state is now allowed to be
restored only once and is then invalidated.  That doesn't seem to make
sense because the saved state should be good enough to be reused.

Soon after, drivers began to work around this behavior by calling
pci_save_state() immediately after pci_restore_state(), see e.g. commit
b94f2d775a ("igb: call pci_save_state after pci_restore_state").
Hilariously, two drivers even set the "saved_state" flag to true before
invoking pci_restore_state(), see ipr_reset_restore_cfg_space() and
e1000_io_slot_reset().

Despite these workarounds, recoverability at all times is not guaranteed:
E.g. when a PCIe port goes through a runtime suspend and resume cycle,
the "saved_state" flag is cleared by:

  pci_pm_runtime_resume()
    pci_pm_default_resume_early()
      pci_restore_state()

... and hence on a subsequent AER event, the port's Config Space cannot be
restored.  Riana reports a recovery failure of a GPU-integrated PCIe
switch and has root-caused it to the behavior of pci_restore_state().
Another workaround would be necessary, namely calling pci_save_state() in
pcie_port_device_runtime_resume().

The motivation of commit c82f63e411 was to prevent restoring state if
pci_save_state() hasn't been called before.  But that can be achieved by
saving state already on device addition, after Config Space has been
initialized.  A desirable side effect is that devices become recoverable
even if no driver gets bound.  This renders the commit unnecessary, so
revert it.

Reported-by: Riana Tauro <riana.tauro@intel.com> # off-list
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Riana Tauro <riana.tauro@intel.com>
Reviewed-by: Rafael J. Wysocki (Intel) <rafael@kernel.org>
Link: https://patch.msgid.link/9e34ce61c5404e99ffdd29205122c6fb334b38aa.1763483367.git.lukas@wunner.de
Cc: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-02-11 13:40:17 +01:00
arch ARM: 9468/1: fix memset64() on big-endian 2026-02-11 13:40:16 +01:00
block block: fix NULL pointer dereference in blk_zone_reset_all_bio_endio() 2026-01-08 10:15:06 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:28:39 +01:00
Documentation fou: Don't allow 0 for FOU_ATTR_IPPROTO. 2026-01-30 10:28:39 +01:00
drivers PCI/ERR: Ensure error recoverability at all times 2026-02-11 13:40:17 +01:00
fs ceph: fix oops due to invalid pointer for kfree() in parse_longname() 2026-02-11 13:40:17 +01:00
include ceph: fix NULL pointer dereference in ceph_mds_auth_match() 2026-02-11 13:40:16 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/io-wq: check IO_WQ_BIT_EXIT inside work run loop 2026-01-30 10:28:41 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel perf: sched: Fix perf crash with new is_user_task() helper 2026-02-06 16:55:50 +01:00
lib flex_proportions: make fprop_new_period() hardirq safe 2026-02-06 16:55:46 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm, shmem: prevent infinite loop on truncate race 2026-02-11 13:40:17 +01:00
net mptcp: avoid dup SUB_CLOSED events after disconnect 2026-02-06 16:55:50 +01:00
rust rust: rbtree: fix documentation typo in CursorMut peek_next method 2026-02-06 16:55:44 +01:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:14:50 +01:00
scripts scripts: generate_rust_analyzer: Add compiler_builtins -> core dep 2026-02-06 16:55:47 +01:00
security keys/trusted_keys: fix handle passed to tpm_buf_append_name during unseal 2026-01-30 10:28:44 +01:00
sound ALSA: aloop: Fix racy access at PCM trigger 2026-02-11 13:40:15 +01:00
tools bpf/selftests: test_select_reuseport_kern: Remove unused header 2026-02-06 16:55:51 +01:00
usr kbuild: uapi: Strip comments before size type check 2025-11-13 15:34:35 -05:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:40:17 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:25:02 +09:00
Makefile Linux 6.12.69 2026-02-06 16:55:51 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.