[RFC PATCH v5 0/5] Improve the performance of RISC-V vector unit-stride/whole register ld/st instructions

[Max Chou]

Hi,

This version provides subroutine to iterate the load/store operations
per page and replaces the original continuous load/store loop by the
memcpy call.

And thank for Richard Henderson's patch set to the user-only munmap
race issue, this version rebases on it and apply the
[set|clear]_helper_retaddr calls.

I'm preparing the v6 version that will include
* Improve the vector unit-stride fault-only-first load instructions
* Try to handle the watchpoints by hand to increase the possibility to
    do host direct access


Some performance result of this version 
1. Test case provided in 
    https://gitlab.com/qemu-project/qemu/-/issues/2137#note_1757501369
    - QEMU user mode (vlen=512):
        - Original:   ~40.1 sec
        - v4:          ~4.7 sec
        - v5:          ~2.9 sec
    - QEMU system mode (vlen=512):
        - Original:  ~112.5 sec
        - v4:          ~6.5 sec
        - v5:          ~3.1 sec
2. SPEC CPU2006 INT (ref input)
    - QEMU user mode (vlen=512)
        - Original:   ~37.4 hr
        - v4:         ~12.2 hr
        - v5:         ~10.0 hr


Based-on: 20240710032814.104643-1-richard.henderson@linaro.org

Changes from v4:
- v4 patch 1
    - Queued
- patch 1
    - Separated from the patch 2 of v4
- patch 2
    - Remove mask bound checking flow
    - Provide a subroutine to iterate pages accessed by the instruction
    - Add [set|clear]_helper_retaddr to avoid the munmap race issue on
      user mode
- patch 3
    - Apply the subroutine to the unit-stride whole register load/store
      instructions
- patch 4
    - Replace the original loop by memcpy call when the endian of both
      host and guest are the same

Previous version:
- v1: https://lore.kernel.org/all/20240215192823.729209-1-max.chou@sifive.com/
- v2: https://lore.kernel.org/all/20240531174504.281461-1-max.chou@sifive.com/
- v3: https://lore.kernel.org/all/20240613141906.1276105-1-max.chou@sifive.com/
- v4: https://lore.kernel.org/all/20240613175122.1299212-1-max.chou@sifive.com/

Max Chou (5):
  target/riscv: Set vdata.vm field for vector load/store whole register
    instructions
  target/riscv: rvv: Provide a fast path using direct access to host ram
    for unmasked unit-stride load/store
  target/riscv: rvv: Provide a fast path using direct access to host ram
    for unit-stride whole register load/store
  target/riscv: rvv: Provide group continuous ld/st flow for unit-stride
    ld/st instructions
  target/riscv: Inline unit-stride ld/st and corresponding functions for
    performance

 target/riscv/insn_trans/trans_rvv.c.inc |   3 +
 target/riscv/vector_helper.c            | 482 +++++++++++++++---------
 2 files changed, 307 insertions(+), 178 deletions(-)

-- 
2.34.1