linux-kernel - [RFC V1 0/6] Generic Entry/Exit support for ppc64

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Message-ID: <20250428152225.66044-2-mchauras@linux.ibm.com>
Date: Mon, 28 Apr 2025 20:52:20 +0530
From: Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, naveen@...nel.org,
        neeraj.upadhyay@...nel.org, vschneid@...hat.com, tglx@...utronix.de,
        frederic@...nel.org, ankur.a.arora@...cle.com, sshegde@...ux.ibm.com,
        bigeasy@...utronix.de, kees@...nel.org, oleg@...hat.com,
        peterz@...radead.org, tzimmermann@...e.de, namcao@...utronix.de,
        kan.liang@...ux.intel.com, mcgrof@...nel.org, rppt@...nel.org,
        atrajeev@...ux.vnet.ibm.com, anjalik@...ux.ibm.com,
        coltonlewis@...gle.com, linuxppc-dev@...ts.ozlabs.org,
        Mukesh Kumar Chaurasiya <mchauras@...ux.ibm.com>
Subject: [RFC V1 0/6] Generic Entry/Exit support for ppc64

This is a syscall only implementation of generic entry/exit framework
for framework for ppc. IRQ handling is not done in this RFC. 

This will break the ppc32 build as of now which will be fixed along with
IRQ handling.

Below are the performance benchmarks from perf bench basic syscall.
This is for 1,00,00,000 getppid() calls

| Metric     | Without Generic Framework | With Generic Framework |
| ---------- | ------------------------- | ---------------------- |
| Total time | 0.904 [sec]               | 0.856 [sec]            |
| usecs/op   | 0.090403                  | 0.085638               |
| ops/sec    | 1,10,61,579               | 1,16,77,086            |

That's ~5% degradation as of now.

Mukesh Kumar Chaurasiya (6):
  powerpc: rename arch_irq_disabled_regs
  powerpc: Prepare to build with genreic entry/exit framework
  powerpc: introduce arch_enter_from_user_mode
  powerpc: Add flag in paca for register restore state
  powerpc: Introduce syscall exit arch functions
  powerpc: Enable Generic Entry/Exit for syscalls.

 arch/powerpc/Kconfig                    |   1 +
 arch/powerpc/include/asm/entry-common.h | 158 ++++++++++++++++++++++++
 arch/powerpc/include/asm/hw_irq.h       |   4 +-
 arch/powerpc/include/asm/interrupt.h    | 117 +++++++++++++++++-
 arch/powerpc/include/asm/paca.h         |   1 +
 arch/powerpc/include/asm/stacktrace.h   |   8 ++
 arch/powerpc/include/asm/syscall.h      |   5 +
 arch/powerpc/include/asm/thread_info.h  |   1 +
 arch/powerpc/kernel/interrupt.c         | 153 ++++++-----------------
 arch/powerpc/kernel/ptrace/ptrace.c     | 103 ---------------
 arch/powerpc/kernel/signal.c            |   8 ++
 arch/powerpc/kernel/syscall.c           | 117 +-----------------
 arch/powerpc/kernel/traps.c             |   2 +-
 arch/powerpc/kernel/watchdog.c          |   2 +-
 arch/powerpc/perf/core-book3s.c         |   2 +-
 15 files changed, 336 insertions(+), 346 deletions(-)
 create mode 100644 arch/powerpc/include/asm/entry-common.h

-- 
2.49.0