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Kan Liang bd24f9beed perf/x86/intel: Add a check for dynamic constraints 
The current event scheduler has a limit. If the counter constraint of an
event is not a subset of any other counter constraint with an equal or
higher weight. The counters may not be fully utilized.

To workaround it, the commit bc1738f6ee ("perf, x86: Fix event
scheduler for constraints with overlapping counters") introduced an
overlap flag, which is hardcoded to the event constraint that may
trigger the limit. It only works for static constraints.

Many features on and after Intel PMON v6 require dynamic constraints. An
event constraint is decided by both static and dynamic constraints at
runtime. See commit 4dfe3232cc ("perf/x86: Add dynamic constraint").
The dynamic constraints are from CPUID enumeration. It's impossible to
hardcode it in advance. It's not practical to set the overlap flag to all
events. It's harmful to the scheduler.

For the existing Intel platforms, the dynamic constraints don't trigger
the limit. A real fix is not required.

However, for virtualization, VMM may give a weird CPUID enumeration to a
guest. It's impossible to indicate what the weird enumeration is. A
check is introduced, which can list the possible breaks if a weird
enumeration is used.

Check the dynamic constraints enumerated for normal, branch counters
logging, and auto-counter reload.
Check both PEBS and non-PEBS constratins.

Closes: https://lore.kernel.org/lkml/20250416195610.GC38216@noisy.programming.kicks-ass.net/
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250512175542.2000708-1-kan.liang@linux.intel.com
History 2025-11-07 15:08:23 +01:00
arch perf/x86/intel: Add a check for dynamic constraints 2025-11-07 15:08:23 +01:00
block block-6.18-20251009 2025-10-10 10:37:13 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation RTC for 6.18 2025-10-11 11:56:47 -07:00
drivers i2c-for-6.18-rc1-hotfix 2025-10-12 13:27:56 -07:00
fs - Avoid -Wflex-array-member-not-at-end warnings 2025-10-10 14:06:02 -07:00
include entry,unwind/deferred: Fix unwind_reset_info() placement 2025-11-05 13:57:32 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: increment fallback loop src offset 2025-10-08 07:26:14 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel perf: Support deferred user unwind 2025-10-29 10:29:58 +01:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab hotfix for 6.18-rc1 2025-10-11 10:40:24 -07:00
net bpf-fixes 2025-10-11 10:31:38 -07:00
rust 7 hotfixes. All 7 are cc:stable and all 7 are for MM. 2025-10-11 10:14:55 -07:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound sound fixes for 6.18-rc1 2025-10-10 09:55:19 -07:00
tools perf: Support deferred user unwind 2025-10-29 10:29:58 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt hyperv-next for v6.18 2025-10-07 08:40:15 -07:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.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 MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap MAINTAINERS, .mailmap: update Umang's email address 2025-10-07 13:48:55 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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 USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Just one series here - Mike Rappoport has taught KEXEC handover to 2025-10-11 10:27:52 -07:00
Makefile Linux 6.18-rc1 2025-10-12 13:42:36 -07:00
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.