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authorPuranjay Mohan <puranjay@kernel.org>2024-05-02 15:18:51 +0000
committerAlexei Starovoitov <ast@kernel.org>2024-05-12 16:54:34 -0700
commit19c56d4e5be102cd118162b9f72d9c6d353e76fc (patch)
tree0b3078b5e18ca50af611fc29c79cb0222405853e /arch
parentf122668ddcce450c2585f0be4bf4478d6fd6176b (diff)
riscv, bpf: add internal-only MOV instruction to resolve per-CPU addrs
Support an instruction for resolving absolute addresses of per-CPU data from their per-CPU offsets. This instruction is internal-only and users are not allowed to use them directly. They will only be used for internal inlining optimizations for now between BPF verifier and BPF JITs. RISC-V uses generic per-cpu implementation where the offsets for CPUs are kept in an array called __per_cpu_offset[cpu_number]. RISCV stores the address of the task_struct in TP register. The first element in task_struct is struct thread_info, and we can get the cpu number by reading from the TP register + offsetof(struct thread_info, cpu). Once we have the cpu number in a register we read the offset for that cpu from address: &__per_cpu_offset + cpu_number << 3. Then we add this offset to the destination register. To measure the improvement from this change, the benchmark in [1] was used on Qemu: Before: glob-arr-inc : 1.127 ± 0.013M/s arr-inc : 1.121 ± 0.004M/s hash-inc : 0.681 ± 0.052M/s After: glob-arr-inc : 1.138 ± 0.011M/s arr-inc : 1.366 ± 0.006M/s hash-inc : 0.676 ± 0.001M/s [1] https://github.com/anakryiko/linux/commit/8dec900975ef Signed-off-by: Puranjay Mohan <puranjay@kernel.org> Acked-by: Björn Töpel <bjorn@kernel.org> Link: https://lore.kernel.org/r/20240502151854.9810-2-puranjay@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/riscv/net/bpf_jit_comp64.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 15e482f2c657..1f0159963b3e 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -12,6 +12,7 @@
#include <linux/stop_machine.h>
#include <asm/patch.h>
#include <asm/cfi.h>
+#include <asm/percpu.h>
#include "bpf_jit.h"
#define RV_FENTRY_NINSNS 2
@@ -1089,6 +1090,24 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
emit_or(RV_REG_T1, rd, RV_REG_T1, ctx);
emit_mv(rd, RV_REG_T1, ctx);
break;
+ } else if (insn_is_mov_percpu_addr(insn)) {
+ if (rd != rs)
+ emit_mv(rd, rs, ctx);
+#ifdef CONFIG_SMP
+ /* Load current CPU number in T1 */
+ emit_ld(RV_REG_T1, offsetof(struct thread_info, cpu),
+ RV_REG_TP, ctx);
+ /* << 3 because offsets are 8 bytes */
+ emit_slli(RV_REG_T1, RV_REG_T1, 3, ctx);
+ /* Load address of __per_cpu_offset array in T2 */
+ emit_addr(RV_REG_T2, (u64)&__per_cpu_offset, extra_pass, ctx);
+ /* Add offset of current CPU to __per_cpu_offset */
+ emit_add(RV_REG_T1, RV_REG_T2, RV_REG_T1, ctx);
+ /* Load __per_cpu_offset[cpu] in T1 */
+ emit_ld(RV_REG_T1, 0, RV_REG_T1, ctx);
+ /* Add the offset to Rd */
+ emit_add(rd, rd, RV_REG_T1, ctx);
+#endif
}
if (imm == 1) {
/* Special mov32 for zext */
@@ -2038,3 +2057,8 @@ bool bpf_jit_supports_arena(void)
{
return true;
}
+
+bool bpf_jit_supports_percpu_insn(void)
+{
+ return true;
+}