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K Prateek Nayak 01e528e63c x86/cpu/topology: Always try cpu_parse_topology_ext() on AMD/Hygon 
commit cba4262a19 upstream.

Support for parsing the topology on AMD/Hygon processors using CPUID leaf 0xb
was added in

  3986a0a805 ("x86/CPU/AMD: Derive CPU topology from CPUID function 0xB when available").

In an effort to keep all the topology parsing bits in one place, this commit
also introduced a pseudo dependency on the TOPOEXT feature to parse the CPUID
leaf 0xb.

The TOPOEXT feature (CPUID 0x80000001 ECX[22]) advertises the support for
Cache Properties leaf 0x8000001d and the CPUID leaf 0x8000001e EAX for
"Extended APIC ID" however support for 0xb was introduced alongside the x2APIC
support not only on AMD [1], but also historically on x86 [2].

Similar to 0xb, the support for extended CPU topology leaf 0x80000026 too does
not depend on the TOPOEXT feature.

The support for these leaves is expected to be confirmed by ensuring

  leaf <= {extended_}cpuid_level

and then parsing the level 0 of the respective leaf to confirm EBX[15:0]
(LogProcAtThisLevel) is non-zero as stated in the definition of
"CPUID_Fn0000000B_EAX_x00 [Extended Topology Enumeration]
(Core::X86::Cpuid::ExtTopEnumEax0)" in Processor Programming Reference (PPR)
for AMD Family 19h Model 01h Rev B1 Vol1 [3] Sec. 2.1.15.1 "CPUID Instruction
Functions".

This has not been a problem on baremetal platforms since support for TOPOEXT
(Fam 0x15 and later) predates the support for CPUID leaf 0xb (Fam 0x17[Zen2]
and later), however, for AMD guests on QEMU, the "x2apic" feature can be
enabled independent of the "topoext" feature where QEMU expects topology and
the initial APICID to be parsed using the CPUID leaf 0xb (especially when
number of cores > 255) which is populated independent of the "topoext" feature
flag.

Unconditionally call cpu_parse_topology_ext() on AMD and Hygon processors to
first parse the topology using the XTOPOLOGY leaves (0x80000026 / 0xb) before
using the TOPOEXT leaf (0x8000001e).

While at it, break down the single large comment in parse_topology_amd() to
better highlight the purpose of each CPUID leaf.

Fixes: 3986a0a805 ("x86/CPU/AMD: Derive CPU topology from CPUID function 0xB when available")
Suggested-by: Naveen N Rao (AMD) <naveen@kernel.org>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org # Only v6.9 and above; depends on x86 topology rewrite
Link: https://lore.kernel.org/lkml/1529686927-7665-1-git-send-email-suravee.suthikulpanit@amd.com/ [1]
Link: https://lore.kernel.org/lkml/20080818181435.523309000@linux-os.sc.intel.com/ [2]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 [3]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-09-19 16:35:51 +02:00
arch x86/cpu/topology: Always try cpu_parse_topology_ext() on AMD/Hygon 2025-09-19 16:35:51 +02:00
block block: add a queue_limits_commit_update_frozen helper 2025-09-09 18:58:24 +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 docs: networking: can: change bcm_msg_head frames member to support flexible array 2025-09-19 16:35:49 +02:00
drivers phy: ti-pipe3: fix device leak at unbind 2025-09-19 16:35:51 +02:00
fs btrfs: fix corruption reading compressed range when block size is smaller than page size 2025-09-19 16:35:47 +02:00
include netfilter: nf_tables: make nft_set_do_lookup available unconditionally 2025-09-19 16:35:50 +02:00
init io_uring: fix breakage in EXPERT menu 2025-08-15 12:13:32 +02:00
io_uring io_uring/msg_ring: ensure io_kiocb freeing is deferred for RCU 2025-09-09 18:58:15 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel hrtimers: Unconditionally update target CPU base after offline timer migration 2025-09-19 16:35:47 +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 Disable SLUB_TINY for build testing 2025-09-19 16:35:48 +02:00
net hsr: use hsr_for_each_port_rtnl in hsr_port_get_hsr 2025-09-19 16:35:50 +02:00
rust rust: alloc: fix rusttest by providing Cmalloc::aligned_layout too 2025-08-28 16:31:13 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts rust: support Rust >= 1.91.0 target spec 2025-09-09 18:58:22 +02:00
security apparmor: Fix 8-byte alignment for initial dfa blob streams 2025-08-28 16:30:56 +02:00
sound ALSA: hda/realtek: Fix built-in mic assignment on ASUS VivoBook X515UA 2025-09-19 16:35:43 +02:00
tools tools: gpio: remove the include directory on make clean 2025-09-09 18:58:25 +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 6.12.47 2025-09-11 17:21:47 +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.