Le 17/11/2025 à 07:52, Saket Kumar Bhaskar a écrit :
Inline the calls to bpf_get_smp_processor_id()/bpf_get_current_task()
in the powerpc bpf jit.
powerpc saves the Logical processor number (paca_index) and pointer
to current task (__current) in paca.
Here is how the powerpc JITed assembly changes after this commit:
Before:
cpu = bpf_get_smp_processor_id();
addis 12, 2, -517
addi 12, 12, -29456
mtctr 12
bctrl
mr 8, 3
After:
cpu = bpf_get_smp_processor_id();
lhz 8, 8(13)
To evaluate the performance improvements introduced by this change,
the benchmark described in [1] was employed.
+---------------+-------------------+-------------------+--------------+
| Name | Before | After | % change |
|---------------+-------------------+-------------------+--------------|
| glob-arr-inc | 40.701 ± 0.008M/s | 55.207 ± 0.021M/s | + 35.64% |
| arr-inc | 39.401 ± 0.007M/s | 56.275 ± 0.023M/s | + 42.42% |
| hash-inc | 24.944 ± 0.004M/s | 26.212 ± 0.003M/s | + 5.08% |
+---------------+-------------------+-------------------+--------------+
[1]
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fanakryiko%2Flinux%2Fcommit%2F8dec900975ef&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4a08a3af41ff4f9bc55d08de25a5f0ee%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638989591794687135%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=FtfTYpm9VgLfO1Q3iZvyrE4QRG317%2B%2BjfPd66Wd%2FQP4%3D&reserved=0
Signed-off-by: Saket Kumar Bhaskar <[email protected]>
---
arch/powerpc/net/bpf_jit_comp.c | 11 +++++++++++
arch/powerpc/net/bpf_jit_comp64.c | 10 ++++++++++
2 files changed, 21 insertions(+)
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 2f2230ae2145..c88dfa1418ec 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -471,6 +471,17 @@ bool bpf_jit_supports_percpu_insn(void)
return IS_ENABLED(CONFIG_PPC64);
}
+bool bpf_jit_inlines_helper_call(s32 imm)
+{
+ switch (imm) {
+ case BPF_FUNC_get_smp_processor_id:
+ case BPF_FUNC_get_current_task:
What about BPF_FUNC_get_current_task_btf ?
+ return true;
+ default:
+ return false;
+ }
+}
+
void *arch_alloc_bpf_trampoline(unsigned int size)
{
return bpf_prog_pack_alloc(size, bpf_jit_fill_ill_insns);
diff --git a/arch/powerpc/net/bpf_jit_comp64.c
b/arch/powerpc/net/bpf_jit_comp64.c
index 21486706b5ea..4e1643422370 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -1399,6 +1399,16 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
u32 *fimage, struct code
case BPF_JMP | BPF_CALL:
ctx->seen |= SEEN_FUNC;
+ if (insn[i].src_reg == BPF_REG_0) {
Are you sure you want to use BPF_REG_0 here ? Is it the correct meaning
? I see RISCV and ARM64 use 0 instead.
If you keep BPF_REG_0 I would have a preference for
if (src_reg == bpf_to_ppc(BPF_REG_0))
+ if (imm == BPF_FUNC_get_smp_processor_id) {
+ EMIT(PPC_RAW_LHZ(insn[i].src_reg, _R13,
offsetof(struct paca_struct, paca_index)));
This looks wrong, you can't use insn[i].src_reg to emit powerpc
instructions, you must use the local src_reg which converts the register
ID with bpf_to_ppc()
+ break;
+ } else if (imm == BPF_FUNC_get_current_task) {
+ EMIT(PPC_RAW_LD(insn[i].src_reg, _R13,
offsetof(struct paca_struct, __current)));
Same here.
+ break;
+ }
+ }
+
ret = bpf_jit_get_func_addr(fp, &insn[i], extra_pass,
&func_addr,
&func_addr_fixed);
if (ret < 0)
