diff options
| author | Andy Chiu <andy.chiu@sifive.com> | 2024-01-15 05:59:24 +0000 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-01-16 07:13:57 -0800 |
| commit | c2a658d419246108c9bf065ec347355de5ba8a05 (patch) | |
| tree | 01afac13dfa6c595dd5154b3f45a2a6fe929f728 /arch/riscv/Kconfig | |
| parent | 7df56cbc27e4239807b5d8860f79a7350d63a741 (diff) | |
riscv: lib: vectorize copy_to_user/copy_from_user
This patch utilizes Vector to perform copy_to_user/copy_from_user. If
Vector is available and the size of copy is large enough for Vector to
perform better than scalar, then direct the kernel to do Vector copies
for userspace. Though the best programming practice for users is to
reduce the copy, this provides a faster variant when copies are
inevitable.
The optimal size for using Vector, copy_to_user_thres, is only a
heuristic for now. We can add DT parsing if people feel the need of
customizing it.
The exception fixup code of the __asm_vector_usercopy must fallback to
the scalar one because accessing user pages might fault, and must be
sleepable. Current kernel-mode Vector does not allow tasks to be
preemptible, so we must disactivate Vector and perform a scalar fallback
in such case.
The original implementation of Vector operations comes from
https://github.com/sifive/sifive-libc, which we agree to contribute to
Linux kernel.
Co-developed-by: Jerry Shih <jerry.shih@sifive.com>
Signed-off-by: Jerry Shih <jerry.shih@sifive.com>
Co-developed-by: Nick Knight <nick.knight@sifive.com>
Signed-off-by: Nick Knight <nick.knight@sifive.com>
Suggested-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20240115055929.4736-6-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/Kconfig')
| -rw-r--r-- | arch/riscv/Kconfig | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 95a2a06acc6a..3c5ba05e8a2d 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -525,6 +525,14 @@ config RISCV_ISA_V_DEFAULT_ENABLE If you don't know what to do here, say Y. +config RISCV_ISA_V_UCOPY_THRESHOLD + int "Threshold size for vectorized user copies" + depends on RISCV_ISA_V + default 768 + help + Prefer using vectorized copy_to_user()/copy_from_user() when the + workload size exceeds this value. + config TOOLCHAIN_HAS_ZBB bool default y |