linux-kernel - [PATCH v2 0/6] x86: Rewrite switch

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Date:	Sat, 18 Jun 2016 16:56:12 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2 0/6] x86: Rewrite switch_to()

This patch set simplifies the switch_to() code, by moving the stack switch
code out of line into an asm stub before calling __switch_to().  This ends
up being more readable, and using the C calling convention instead of
clobbering all registers improves code generation.  It also allows newly
forked processes to construct a special stack frame to seamlessly flow
to ret_from_fork, instead of using a test and branch, or an unbalanced
call/ret.

Changes from v1:
- Added struct inactive_task_frame
- Added comments about kernel threads returning to userspace
- Cleaned up some incorrect uses of thread.sp

Brian Gerst (6):
      x86-32, kgdb: Don't use thread.ip in sleeping_thread_to_gdb_regs()
      x86-64, kgdb: clear GDB_PS on 64-bit
      x86: Add struct inactive_task_frame
      x86: Rewrite switch_to() code
      x86: Pass kernel thread parameters in fork_frame
      x86: Fix thread_saved_pc()

 arch/x86/entry/entry_32.S          |  68 +++++++++++++-----
 arch/x86/entry/entry_64.S          |  76 ++++++++++++++------
 arch/x86/include/asm/processor.h   |  13 +---
 arch/x86/include/asm/stacktrace.h  |   4 +-
 arch/x86/include/asm/switch_to.h   | 142 +++++++------------------------------
 arch/x86/include/asm/thread_info.h |   2 -
 arch/x86/kernel/asm-offsets.c      |   6 ++
 arch/x86/kernel/asm-offsets_32.c   |   5 ++
 arch/x86/kernel/asm-offsets_64.c   |   5 ++
 arch/x86/kernel/kgdb.c             |   8 +--
 arch/x86/kernel/process.c          |  13 +++-
 arch/x86/kernel/process_32.c       |  29 +++-----
 arch/x86/kernel/process_64.c       |  19 ++---
 arch/x86/kernel/smpboot.c          |   1 -
 14 files changed, 187 insertions(+), 204 deletions(-)