linux-kernel - [PATCH 00/10, -v4] x86/fpu: Remove thread::fpu

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Date: Sat,  8 Jun 2024 09:31:25 +0200
From: Ingo Molnar <mingo@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave@...1.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Uros Bizjak <ubizjak@...il.com>
Subject: [PATCH 00/10, -v4] x86/fpu: Remove thread::fpu

This series is one of the dependencies of the fast-headers work,
which aims to reduce header complexity by removing <asm/processor.h>
from the <linux/sched.h> dependency chain, which headers are headers
are fat enough already even if we do not combine them.

To achieve that decoupling, one of the key steps is to not embedd any
C types from <asm/processor.h> into task_struct.

The only architecture that relies on that in a serious fashion is x86,
via the 'struct thread::fpu' variable size structure. The series below
attempts to resolve it by using a calculated fpu context area address
value via the x86_task_fpu() helper. The allocation layout of
task_struct + fpu-save-area doesn't change.

Changes in -v3:

 - Restructure the series to be easier to review
 - Extend the debug checks to all PF_KTHREAD tasks
 - A few cleanups on top

The Git tree can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.x86/fpu

Thanks,

    Ingo

======================>

Ingo Molnar (9):
      x86/fpu: Introduce the x86_task_fpu() helper method
      x86/fpu: Convert task_struct::thread.fpu accesses to use x86_task_fpu()
      x86/fpu: Make task_struct::thread constant size
      x86/fpu: Remove the thread::fpu pointer
      x86/fpu: Push 'fpu' pointer calculation into the fpu__drop() call
      x86/fpu: Make sure x86_task_fpu() doesn't get called for PF_KTHREAD tasks during exit
      x86/fpu: Remove init_task FPU state dependencies, add debugging warning for PF_KTHREAD tasks
      x86/fpu: Use 'fpstate' variable names consistently
      x86/fpu: Fix stale comment in ex_handler_fprestore()

 arch/x86/include/asm/fpu/api.h   |  2 +-
 arch/x86/include/asm/fpu/sched.h |  4 +-
 arch/x86/include/asm/processor.h | 23 ++++++------
 arch/x86/kernel/fpu/context.h    |  4 +-
 arch/x86/kernel/fpu/core.c       | 80 +++++++++++++++++++++++-----------------
 arch/x86/kernel/fpu/init.c       | 23 +++++++-----
 arch/x86/kernel/fpu/regset.c     | 22 +++++------
 arch/x86/kernel/fpu/signal.c     | 18 ++++-----
 arch/x86/kernel/fpu/xstate.c     | 27 ++++++--------
 arch/x86/kernel/fpu/xstate.h     |  6 +--
 arch/x86/kernel/process.c        |  7 +---
 arch/x86/kernel/signal.c         |  6 +--
 arch/x86/kernel/traps.c          |  2 +-
 arch/x86/math-emu/fpu_aux.c      |  2 +-
 arch/x86/math-emu/fpu_entry.c    |  4 +-
 arch/x86/math-emu/fpu_system.h   |  2 +-
 arch/x86/mm/extable.c            |  2 +-
 include/linux/sched.h            | 13 ++-----
 18 files changed, 126 insertions(+), 121 deletions(-)