linux-kernel - [PATCH v2 00/11] Add a percpu subsection for cache hot data

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Message-ID: <20250226180531.1242429-1-brgerst@gmail.com>
Date: Wed, 26 Feb 2025 13:05:19 -0500
From: Brian Gerst <brgerst@...il.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Uros Bizjak <ubizjak@...il.com>,
	Linus Torvalds <torvalds@...uxfoundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 00/11] Add a percpu subsection for cache hot data

Add a new percpu subsection for data that is frequently accessed and
exclusive to each processor.  This replaces the pcpu_hot struct on x86,
and is available to all architectures and the core kernel.

ffffffff842fa000 D __per_cpu_hot_start
ffffffff842fa000 D hardirq_stack_ptr
ffffffff842fa008 D __ref_stack_chk_guard
ffffffff842fa008 D __stack_chk_guard
ffffffff842fa010 D const_cpu_current_top_of_stack
ffffffff842fa010 D cpu_current_top_of_stack
ffffffff842fa018 D const_current_task
ffffffff842fa018 D current_task
ffffffff842fa020 D __x86_call_depth
ffffffff842fa028 D this_cpu_off
ffffffff842fa030 D __preempt_count
ffffffff842fa034 D cpu_number
ffffffff842fa038 D __softirq_pending
ffffffff842fa03a D hardirq_stack_inuse
ffffffff842fa040 D __per_cpu_hot_end

This applies to the tip/x86/asm branch.

Changes in V2:
- Renamed macros to *_PER_CPU_CACHE_HOT()
- Restored 64-byte limit.
- Added note that this is only to be used by arch and core code.
- Reserve call depth space even when the mitigaion is disabled.
- Use SORT_BY_ALIGNMENT() for dense data packing.
- Remove now unnecessary includes of current.h, fixing up some indirect
  includes.

Brian Gerst (11):
  percpu: Introduce percpu hot section
  x86/percpu: Move pcpu_hot to percpu hot section
  x86/preempt: Move preempt count to percpu hot section
  x86/smp: Move cpu number to percpu hot section
  x86/retbleed: Move call depth to percpu hot section
  x86/softirq: Move softirq_pending to percpu hot section
  x86/irq: Move irq stacks to percpu hot section
  x86/percpu: Move top_of_stack to percpu hot section
  x86/percpu: Move current_task to percpu hot section
  x86/stackprotector: Move __stack_chk_guard to percpu hot section
  x86/smp: Move this_cpu_off to percpu hot section

 arch/x86/entry/entry_32.S             |  4 +--
 arch/x86/entry/entry_64.S             |  6 ++---
 arch/x86/entry/entry_64_compat.S      |  4 +--
 arch/x86/include/asm/current.h        | 36 +++++----------------------
 arch/x86/include/asm/hardirq.h        |  4 +--
 arch/x86/include/asm/irq_stack.h      | 12 ++++-----
 arch/x86/include/asm/nospec-branch.h  | 11 ++++----
 arch/x86/include/asm/percpu.h         |  4 +--
 arch/x86/include/asm/preempt.h        | 25 ++++++++++---------
 arch/x86/include/asm/processor.h      | 15 +++++++++--
 arch/x86/include/asm/smp.h            |  7 +++---
 arch/x86/include/asm/stackprotector.h |  2 +-
 arch/x86/kernel/asm-offsets.c         |  5 ----
 arch/x86/kernel/cpu/common.c          | 25 +++++++++++++------
 arch/x86/kernel/dumpstack_32.c        |  4 +--
 arch/x86/kernel/dumpstack_64.c        |  2 +-
 arch/x86/kernel/head_64.S             |  4 +--
 arch/x86/kernel/irq.c                 |  8 ++++++
 arch/x86/kernel/irq_32.c              | 12 +++++----
 arch/x86/kernel/irq_64.c              |  6 ++---
 arch/x86/kernel/process_32.c          |  6 ++---
 arch/x86/kernel/process_64.c          |  6 ++---
 arch/x86/kernel/setup_percpu.c        |  7 ++++--
 arch/x86/kernel/smpboot.c             |  4 +--
 arch/x86/kernel/vmlinux.lds.S         |  6 ++++-
 arch/x86/lib/retpoline.S              |  2 +-
 include/asm-generic/vmlinux.lds.h     | 10 ++++++++
 include/linux/percpu-defs.h           | 12 +++++++++
 include/linux/preempt.h               |  1 +
 kernel/bpf/verifier.c                 |  4 +--
 scripts/gdb/linux/cpus.py             |  2 +-
 31 files changed, 145 insertions(+), 111 deletions(-)


base-commit: 79165720f31868d9a9f7e5a50a09d5fe510d1822
-- 
2.48.1