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René Rebe 438f9673f3 ACPI: processor_core: fix map_x2apic_id for amd-pstate on am4 
[ Upstream commit 17e7972979 ]

On all AMD AM4 systems I have seen, e.g ASUS X470-i, Pro WS X570 Ace
and equivalent Gigabyte, amd-pstate does not initialize when the
x2apic is enabled in the BIOS. Kernel debug messages include:

[    0.315438] acpi LNXCPU:00: Failed to get CPU physical ID.
[    0.354756] ACPI CPPC: No CPC descriptor for CPU:0
[    0.714951] amd_pstate: the _CPC object is not present in SBIOS or ACPI disabled

I tracked this down to map_x2apic_id() checking device_declaration
passed in via the type argument of acpi_get_phys_id() via
map_madt_entry() while map_lapic_id() does not.

It appears these BIOSes use Processor statements for declaring the CPUs
in the ACPI namespace instead of processor device objects (which should
have been used). CPU declarations via Processor statements were
deprecated in ACPI 6.0 that was released 10 years ago. They should not
be used any more in any contemporary platform firmware.

I tried to contact Asus support multiple times, but never received a
reply nor did any BIOS update ever change this.

Fix amd-pstate w/ x2apic on am4 by allowing map_x2apic_id() to work with
CPUs declared via Processor statements for IDs less than 255, which is
consistent with ACPI 5.0 that still allowed Processor statements to be
used for declaring CPUs.

Fixes: 7237d3de78 ("x86, ACPI: add support for x2apic ACPI extensions")
Signed-off-by: René Rebe <rene@exactco.de>
[ rjw: Changelog edits ]
Link: https://patch.msgid.link/20251126.165513.1373131139292726554.rene@exactco.de
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-12-18 13:55:09 +01:00
arch um: Don't rename vmap to kernel_vmap 2025-12-18 13:55:06 +01:00
block block/blk-throttle: Fix throttle slice time for SSDs 2025-12-18 13:55:00 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: asymmetric_keys - prevent overflow in asymmetric_key_generate_id 2025-12-18 13:54:47 +01:00
Documentation dt-bindings: PCI: amlogic: Fix the register name of the DBI region 2025-12-18 13:54:55 +01:00
drivers ACPI: processor_core: fix map_x2apic_id for amd-pstate on am4 2025-12-18 13:55:09 +01:00
fs gfs2: Prevent recursive memory reclaim 2025-12-18 13:55:08 +01:00
include backlight: lp855x: Fix lp855x.h kernel-doc warnings 2025-12-18 13:55:07 +01:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/napi: fix io_napi_entry RCU accesses 2025-11-24 10:36:06 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel cpuset: Treat cpusets in attaching as populated 2025-12-18 13:55:03 +01:00
lib lib/vsprintf: Check pointer before dereferencing in time_and_date() 2025-12-18 13:54:57 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/huge_memory: fix NULL pointer deference when splitting folio 2025-12-07 06:25:02 +09:00
net wifi: mac80211: fix CMAC functions not handling errors 2025-12-18 13:55:02 +01:00
rust rust: kbuild: workaround rustdoc doctests modifier bug 2025-11-24 10:36:07 +01:00
samples samples: work around glibc redefining some of our defines wrong 2025-12-12 18:37:21 +01:00
scripts kconfig/nconf: Initialize the default locale at startup 2025-12-01 11:43:36 +01:00
security ima: Handle error code returned by ima_filter_rule_match() 2025-12-18 13:55:04 +01:00
sound ASoC: fsl_xcvr: clear the channel status control memory 2025-12-18 13:55:08 +01:00
tools selftests/bpf: Improve reliability of test_perf_branches_no_hw() 2025-12-18 13:55:05 +01:00
usr kbuild: uapi: Strip comments before size type check 2025-11-13 15:34:35 -05:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-24 10:36:06 +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 6.12.62 2025-12-12 18:37:22 +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.