2024-05-19 05:02:08

by Wang, Xiao W

Subject: [PATCH] riscv, bpf: try RVC for reg move within BPF_CMPXCHG JIT

We could try to emit compressed insn for reg move operation during CMPXCHG
JIT, the instruction compression has no impact on the jump offsets of
following forward and backward jump instructions.

Signed-off-by: Xiao Wang <[email protected]>
---
arch/riscv/net/bpf_jit_comp64.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index aac190085472..c134aaec4295 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -531,8 +531,10 @@ static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
/* r0 = atomic_cmpxchg(dst_reg + off16, r0, src_reg); */
case BPF_CMPXCHG:
r0 = bpf_to_rv_reg(BPF_REG_0, ctx);
- emit(is64 ? rv_addi(RV_REG_T2, r0, 0) :
- rv_addiw(RV_REG_T2, r0, 0), ctx);
+ if (is64)
+ emit_mv(RV_REG_T2, r0, ctx);
+ else
+ emit_addiw(RV_REG_T2, r0, 0, ctx);
emit(is64 ? rv_lr_d(r0, 0, rd, 0, 0) :
rv_lr_w(r0, 0, rd, 0, 0), ctx);
jmp_offset = ninsns_rvoff(8);
--
2.25.1

2024-05-21 16:36:25

by Björn Töpel

Subject: Re: [PATCH] riscv, bpf: try RVC for reg move within BPF_CMPXCHG JIT

Xiao Wang <[email protected]> writes:

> We could try to emit compressed insn for reg move operation during CMPXCHG
> JIT, the instruction compression has no impact on the jump offsets of
> following forward and backward jump instructions.

..and at some point we should start supporting Zacas and friends,
instead of lr/sc.

> Signed-off-by: Xiao Wang <[email protected]>

Acked-by: Björn Töpel <[email protected]>

2024-05-24 15:50:38

by patchwork-bot+netdevbpf

Subject: Re: [PATCH] riscv, bpf: try RVC for reg move within BPF_CMPXCHG JIT

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:

On Sun, 19 May 2024 13:05:07 +0800 you wrote:
> We could try to emit compressed insn for reg move operation during CMPXCHG
> JIT, the instruction compression has no impact on the jump offsets of
> following forward and backward jump instructions.
>
> Signed-off-by: Xiao Wang <[email protected]>
> ---
> arch/riscv/net/bpf_jit_comp64.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)

Here is the summary with links:
- riscv, bpf: try RVC for reg move within BPF_CMPXCHG JIT
https://git.kernel.org/bpf/bpf-next/c/99fa63d9ca60

You are awesome, thank you!
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