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Filename Latest commit message Latest commit date
Zhang Rui 4e5a7181a6 x86/topology: Fix erroneous smp_num_siblings on Intel Hybrid platforms
commit edc0a2b5957652f4685ef3516f519f84807087db upstream.

Traditionally, all CPUs in a system have identical numbers of SMT
siblings.  That changes with hybrid processors where some logical CPUs
have a sibling and others have none.

Today, the CPU boot code sets the global variable smp_num_siblings when
every CPU thread is brought up. The last thread to boot will overwrite
it with the number of siblings of *that* thread. That last thread to
boot will "win". If the thread is a Pcore, smp_num_siblings == 2.  If it
is an Ecore, smp_num_siblings == 1.

smp_num_siblings describes if the *system* supports SMT.  It should
specify the maximum number of SMT threads among all cores.

Ensure that smp_num_siblings represents the system-wide maximum number
of siblings by always increasing its value. Never allow it to decrease.

On MeteorLake-P platform, this fixes a problem that the Ecore CPUs are
not updated in any cpu sibling map because the system is treated as an
UP system when probing Ecore CPUs.

Below shows part of the CPU topology information before and after the
fix, for both Pcore and Ecore CPU (cpu0 is Pcore, cpu 12 is Ecore).
...
-/sys/devices/system/cpu/cpu0/topology/package_cpus:000fff
-/sys/devices/system/cpu/cpu0/topology/package_cpus_list:0-11
+/sys/devices/system/cpu/cpu0/topology/package_cpus:3fffff
+/sys/devices/system/cpu/cpu0/topology/package_cpus_list:0-21
...
-/sys/devices/system/cpu/cpu12/topology/package_cpus:001000
-/sys/devices/system/cpu/cpu12/topology/package_cpus_list:12
+/sys/devices/system/cpu/cpu12/topology/package_cpus:3fffff
+/sys/devices/system/cpu/cpu12/topology/package_cpus_list:0-21

Notice that the "before" 'package_cpus_list' has only one CPU.  This
means that userspace tools like lscpu will see a little laptop like
an 11-socket system:

-Core(s) per socket:  1
-Socket(s):           11
+Core(s) per socket:  16
+Socket(s):           1

This is also expected to make the scheduler do rather wonky things
too.

[ dhansen: remove CPUID detail from changelog, add end user effects ]

CC: stable@kernel.org
Fixes: bbb65d2d36 ("x86: use cpuid vector 0xb when available for detecting cpu topology")
Fixes: 95f3d39ccf ("x86/cpu/topology: Provide detect_extended_topology_early()")
Suggested-by: Len Brown <len.brown@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20230323015640.27906-1-rui.zhang%40intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-05-30 12:44:09 +01:00
arch x86/topology: Fix erroneous smp_num_siblings on Intel Hybrid platforms 2023-05-30 12:44:09 +01:00
block
certs
crypto crypto: drbg - Only fail when jent is unavailable in FIPS mode 2023-05-17 11:35:42 +02:00
Documentation media: uapi: add MEDIA_BUS_FMT_METADATA_FIXED media bus format. 2023-05-17 11:35:36 +02:00
drivers gpio: mockup: Fix mode of debugfs files 2023-05-30 12:44:09 +01:00
fs btrfs: use nofs when cleaning up aborted transactions 2023-05-30 12:44:09 +01:00
include lib/string_helpers: Introduce string_upper() and string_lower() helpers 2023-05-30 12:44:08 +01:00
init
ipc
kernel relayfs: fix out-of-bounds access in relay_file_read 2023-05-17 11:35:58 +02:00
lib lib: cpu_rmap: Avoid use after free on rmap->obj array entries 2023-05-30 12:44:03 +01:00
LICENSES
mm mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock 2023-05-17 11:36:05 +02:00
net netfilter: nf_tables: hold mutex on netns pre_exit path 2023-05-30 12:44:08 +01:00
samples samples/bpf: Fix fout leak in hbm's run_bpf_prog 2023-05-30 12:44:03 +01:00
scripts recordmcount: Fix memory leaks in the uwrite function 2023-05-30 12:44:04 +01:00
security
sound ALSA: hda/realtek: Enable headset onLenovo M70/M90 2023-05-30 12:44:09 +01:00
tools selftests/memfd: Fix unknown type name build failure 2023-05-30 12:44:09 +01:00
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Makefile Linux 5.4.243 2023-05-17 11:36:05 +02:00
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 Restructured Text 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.