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K Prateek Nayak 44bce62994 x86/cpu/topology: Use initial APIC ID from XTOPOLOGY leaf on AMD/HYGON 
commit c2415c407a upstream.

Prior to the topology parsing rewrite and the switchover to the new parsing
logic for AMD processors in

  c749ce393b ("x86/cpu: Use common topology code for AMD"),

the initial_apicid on these platforms was:

- First initialized to the LocalApicId from CPUID leaf 0x1 EBX[31:24].

- Then overwritten by the ExtendedLocalApicId in CPUID leaf 0xb
  EDX[31:0] on processors that supported topoext.

With the new parsing flow introduced in

  f7fb3b2dd9 ("x86/cpu: Provide an AMD/HYGON specific topology parser"),

parse_8000_001e() now unconditionally overwrites the initial_apicid already
parsed during cpu_parse_topology_ext().

Although this has not been a problem on baremetal platforms, on virtualized AMD
guests that feature more than 255 cores, QEMU zeros out the CPUID leaf
0x8000001e on CPUs with CoreID > 255 to prevent collision of these IDs in
EBX[7:0] which can only represent a maximum of 255 cores [1].

This results in the following FW_BUG being logged when booting a guest
with more than 255 cores:

    [Firmware Bug]: CPU 512: APIC ID mismatch. CPUID: 0x0000 APIC: 0x0200

AMD64 Architecture Programmer's Manual Volume 2: System Programming Pub.
24593 Rev. 3.42 [2] Section 16.12 "x2APIC_ID" mentions the Extended
Enumeration leaf 0xb (Fn0000_000B_EDX[31:0])(which was later superseded by the
extended leaf 0x80000026) provides the full x2APIC ID under all circumstances
unlike the one reported by CPUID leaf 0x8000001e EAX which depends on the mode
in which APIC is configured.

Rely on the APIC ID parsed during cpu_parse_topology_ext() from CPUID leaf
0x80000026 or 0xb and only use the APIC ID from leaf 0x8000001e if
cpu_parse_topology_ext() failed (has_topoext is false).

On platforms that support the 0xb leaf (Zen2 or later, AMD guests on
QEMU) or the extended leaf 0x80000026 (Zen4 or later), the
initial_apicid is now set to the value parsed from EDX[31:0].

On older AMD/Hygon platforms that do not support the 0xb leaf but support the
TOPOEXT extension (families 0x15, 0x16, 0x17[Zen1], and Hygon), retain current
behavior where the initial_apicid is set using the 0x8000001e leaf.

Issue debugged by Naveen N Rao (AMD) <naveen@kernel.org> and Sairaj Kodilkar
<sarunkod@amd.com>.

  [ bp: Massage commit message. ]

Fixes: c749ce393b ("x86/cpu: Use common topology code for AMD")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Naveen N Rao (AMD) <naveen@kernel.org>
Cc: stable@vger.kernel.org
Link: 35ac5dfbca [1]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 [2]
Link: https://lore.kernel.org/20250825075732.10694-2-kprateek.nayak@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-09-04 15:31:52 +02:00
arch x86/cpu/topology: Use initial APIC ID from XTOPOLOGY leaf on AMD/HYGON 2025-09-04 15:31:52 +02:00
block block: Introduce bio_needs_zone_write_plugging() 2025-08-20 18:30:51 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: jitter - fix intermediary handling 2025-08-20 18:30:42 +02:00
Documentation dt-bindings: display/msm: qcom,mdp5: drop lut clock 2025-09-04 15:31:48 +02:00
drivers net: macb: Disable clocks once 2025-09-04 15:31:52 +02:00
fs efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare 2025-09-04 15:31:52 +02:00
include net: rose: convert 'use' field to refcount_t 2025-09-04 15:31:51 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/futex: ensure io_futex_wait() cleans up properly on failure 2025-08-28 16:31:05 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel of: reserved_mem: Restructure call site for dma_contiguous_early_fixup() 2025-09-04 15:31:45 +02:00
lib lib/sbitmap: convert shallow_depth from one word to the whole sbitmap 2025-08-20 18:30:49 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/memory-failure: fix infinite UCE for VM_PFNMAP pfn 2025-08-28 16:31:05 +02:00
net l2tp: do not use sock_hold() in pppol2tp_session_get_sock() 2025-09-04 15:31:51 +02:00
rust rust: alloc: fix rusttest by providing Cmalloc::aligned_layout too 2025-08-28 16:31:13 +02:00
samples samples: mei: Fix building on musl libc 2025-08-15 12:13:38 +02:00
scripts kconfig: lxdialog: fix 'space' to (de)select options 2025-08-20 18:30:48 +02:00
security apparmor: Fix 8-byte alignment for initial dfa blob streams 2025-08-28 16:30:56 +02:00
sound ASoC: codecs: tx-macro: correct tx_macro_component_drv name 2025-09-04 15:31:44 +02:00
tools perf symbol-minimal: Fix ehdr reading in filename__read_build_id 2025-09-04 15:31:43 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.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 MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.44 2025-08-28 16:31:16 +02:00
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.