linux-kernel - [PATCH v5 00/22] powerpc/32: Implement C syscall entry/exit

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Date:   Mon,  8 Feb 2021 15:10:19 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com,
        msuchanek@...e.de
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v5 00/22] powerpc/32: Implement C syscall entry/exit

This series implements C syscall entry/exit for PPC32. It reuses
the work already done for PPC64.

This series is based on today's merge-test (b6f72fc05389e3fc694bf5a5fa1bbd33f61879e0)

In terms on performance we have the following number of cycles on an
8xx running null_syscall benchmark:
- mainline: 296 cycles
- after patch 4: 283 cycles
- after patch 16: 304 cycles
- after patch 17: 348 cycles
- at the end of the series: 320 cycles

So in summary, we have a degradation of performance of 8% on null_syscall.

I think it is not a big degradation, it is worth it.

v4 was the first mature version.

v5:
- Comments from Nick
- Converted booke DBCR0 handling in C
- Removed convertion of KUAP restore in C (will be done as part of interrupt entry/exit porting to C)
- Added a few more changes in preparatory patches to prepare for interrupt entry/exit in C which will follow

Christophe Leroy (22):
  powerpc/32s: Add missing call to kuep_lock on syscall entry
  powerpc/32: Always enable data translation on syscall entry
  powerpc/32: On syscall entry, enable instruction translation at the
    same time as data
  powerpc/32: Reorder instructions to avoid using CTR in syscall entry
  powerpc/irq: Add helper to set regs->softe
  powerpc/irq: Rework helpers that manipulate MSR[EE/RI]
  powerpc/irq: Add stub irq_soft_mask_return() for PPC32
  powerpc/syscall: Rename syscall_64.c into interrupt.c
  powerpc/syscall: Make interrupt.c buildable on PPC32
  powerpc/syscall: Use is_compat_task()
  powerpc/syscall: Save r3 in regs->orig_r3
  powerpc/syscall: Change condition to check MSR_RI
  powerpc/32: Always save non volatile GPRs at syscall entry
  powerpc/syscall: implement system call entry/exit logic in C for PPC32
  powerpc/32: Remove verification of MSR_PR on syscall in the ASM entry
  powerpc/syscall: Avoid stack frame in likely part of
    system_call_exception()
  powerpc/syscall: Do not check unsupported scv vector on PPC32
  powerpc/syscall: Remove FULL_REGS verification in
    system_call_exception
  powerpc/syscall: Optimise checks in beginning of
    system_call_exception()
  powerpc/syscall: Avoid storing 'current' in another pointer
  powerpc/32: Remove the counter in global_dbcr0
  powerpc/32: Handle bookE debugging in C in syscall entry/exit

 arch/powerpc/include/asm/hw_irq.h             |  91 +++--
 arch/powerpc/include/asm/ptrace.h             |   5 +
 arch/powerpc/include/asm/reg.h                |   1 +
 arch/powerpc/include/asm/reg_booke.h          |   3 +
 arch/powerpc/kernel/Makefile                  |   4 +-
 arch/powerpc/kernel/entry_32.S                | 321 ++----------------
 arch/powerpc/kernel/entry_64.S                |   2 -
 arch/powerpc/kernel/head_32.h                 |  96 +-----
 arch/powerpc/kernel/head_booke.h              |  51 +--
 .../kernel/{syscall_64.c => interrupt.c}      | 120 +++++--
 arch/powerpc/kernel/syscalls/syscall.tbl      |  20 +-
 11 files changed, 218 insertions(+), 496 deletions(-)
 rename arch/powerpc/kernel/{syscall_64.c => interrupt.c} (80%)

-- 
2.25.0