Merge branch 'bpf-inline-helpers-in-arm64-and-riscv-jits'

Puranjay Mohan says:

====================
bpf: Inline helpers in arm64 and riscv JITs

Changes in v5 -> v6:
arm64 v5: https://lore.kernel.org/all/[email protected]/
riscv v2: https://lore.kernel.org/all/[email protected]/
- Combine riscv and arm64 changes in single series
- Some coding style fixes

Changes in v4 -> v5:
v4: https://lore.kernel.org/all/[email protected]/
- Implement the inlining of the bpf_get_smp_processor_id() in the JIT.

NOTE: This needs to be based on:
https://lore.kernel.org/all/[email protected]/
to be built.

Manual run of bpf-ci with this series rebased on above:
kernel-patches/bpf#6929

Changes in v3 -> v4:
v3: https://lore.kernel.org/all/[email protected]/
- Fix coding style issue related to C89 standards.

Changes in v2 -> v3:
v2: https://lore.kernel.org/all/[email protected]/
- Fixed the xlated dump of percpu mov to "r0 = &(void __percpu *)(r0)"
- Made ARM64 and x86-64 use the same code for inlining. The only difference
  that remains is the per-cpu address of the cpu_number.

Changes in v1 -> v2:
v1: https://lore.kernel.org/all/[email protected]/
- Add a patch to inline bpf_get_smp_processor_id()
- Fix an issue in MRS instruction encoding as pointed out by Will
- Remove CONFIG_SMP check because arm64 kernel always compiles with CONFIG_SMP

This series adds the support of internal only per-CPU instructions and inlines
the bpf_get_smp_processor_id() helper call for ARM64 and RISC-V BPF JITs.

Here is an example of calls to bpf_get_smp_processor_id() and
percpu_array_map_lookup_elem() before and after this series on ARM64.

                                         BPF
                                        =====
              BEFORE                                       AFTER
             --------                                     -------

int cpu = bpf_get_smp_processor_id();           int cpu = bpf_get_smp_processor_id();
(85) call bpf_get_smp_processor_id#229032       (85) call bpf_get_smp_processor_id#8

p = bpf_map_lookup_elem(map, &zero);            p = bpf_map_lookup_elem(map, &zero);
(18) r1 = map[id:78]                            (18) r1 = map[id:153]
(18) r2 = map[id:82][0]+65536                   (18) r2 = map[id:157][0]+65536
(85) call percpu_array_map_lookup_elem#313512   (07) r1 += 496
                                                (61) r0 = *(u32 *)(r2 +0)
                                                (35) if r0 >= 0x1 goto pc+5
                                                (67) r0 <<= 3
                                                (0f) r0 += r1
                                                (79) r0 = *(u64 *)(r0 +0)
                                                (bf) r0 = &(void __percpu *)(r0)
                                                (05) goto pc+1
                                                (b7) r0 = 0

                                      ARM64 JIT
                                     ===========

              BEFORE                                       AFTER
             --------                                     -------

int cpu = bpf_get_smp_processor_id();           int cpu = bpf_get_smp_processor_id();
mov     x10, #0xfffffffffffff4d0                mrs     x10, sp_el0
movk    x10, #0x802b, lsl #16                   ldr     w7, [x10, #24]
movk    x10, #0x8000, lsl #32
blr     x10
add     x7, x0, #0x0

p = bpf_map_lookup_elem(map, &zero);            p = bpf_map_lookup_elem(map, &zero);
mov     x0, #0xffff0003ffffffff                 mov     x0, #0xffff0003ffffffff
movk    x0, #0xce5c, lsl #16                    movk    x0, #0xe0f3, lsl #16
movk    x0, #0xca00                             movk    x0, #0x7c00
mov     x1, #0xffff8000ffffffff                 mov     x1, #0xffff8000ffffffff
movk    x1, #0x8bdb, lsl #16                    movk    x1, #0xb0c7, lsl #16
movk    x1, #0x6000                             movk    x1, #0xe000
mov     x10, #0xffffffffffff3ed0                add     x0, x0, #0x1f0
movk    x10, #0x802d, lsl #16                   ldr     w7, [x1]
movk    x10, #0x8000, lsl #32                   cmp     x7, #0x1
blr     x10                                     b.cs    0x0000000000000090
add     x7, x0, #0x0                            lsl     x7, x7, #3
                                                add     x7, x7, x0
                                                ldr     x7, [x7]
                                                mrs     x10, tpidr_el1
                                                add     x7, x7, x10
                                                b       0x0000000000000094
                                                mov     x7, #0x0

              Performance improvement found using benchmark[1]

./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc

  +---------------+-------------------+-------------------+--------------+
  |      Name     |      Before       |        After      |   % change   |
  |---------------+-------------------+-------------------+--------------|
  | glob-arr-inc  | 23.380 ± 1.675M/s | 25.893 ± 0.026M/s |   + 10.74%   |
  | arr-inc       | 23.928 ± 0.034M/s | 25.213 ± 0.063M/s |   + 5.37%    |
  | hash-inc      | 12.352 ± 0.005M/s | 12.609 ± 0.013M/s |   + 2.08%    |
  +---------------+-------------------+-------------------+--------------+

[1] anakryiko/linux@8dec900975ef

             RISCV64 JIT output for `call bpf_get_smp_processor_id`
            =======================================================

                  Before                           After
                 --------                         -------

           auipc   t1,0x848c                  ld    a5,32(tp)
           jalr    604(t1)
           mv      a5,a0

  Benchmark using [1] on Qemu.

  ./benchs/run_bench_trigger.sh glob-arr-inc arr-inc hash-inc

  +---------------+------------------+------------------+--------------+
  |      Name     |     Before       |       After      |   % change   |
  |---------------+------------------+------------------+--------------|
  | glob-arr-inc  | 1.077 ± 0.006M/s | 1.336 ± 0.010M/s |   + 24.04%   |
  | arr-inc       | 1.078 ± 0.002M/s | 1.332 ± 0.015M/s |   + 23.56%   |
  | hash-inc      | 0.494 ± 0.004M/s | 0.653 ± 0.001M/s |   + 32.18%   |
  +---------------+------------------+------------------+--------------+
====================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Alexei Starovoitov

arch/arm64/include/asm/insn.h

@@ -135,6 +135,12 @@ enum aarch64_insn_special_register {
 	AARCH64_INSN_SPCLREG_SP_EL2	= 0xF210
 };
 
+enum aarch64_insn_system_register {
+	AARCH64_INSN_SYSREG_TPIDR_EL1	= 0x4684,
+	AARCH64_INSN_SYSREG_TPIDR_EL2	= 0x6682,
+	AARCH64_INSN_SYSREG_SP_EL0	= 0x4208,
+};
+
 enum aarch64_insn_variant {
 	AARCH64_INSN_VARIANT_32BIT,
 	AARCH64_INSN_VARIANT_64BIT
@@ -686,6 +692,8 @@ u32 aarch64_insn_gen_cas(enum aarch64_insn_register result,
 }
 #endif
 u32 aarch64_insn_gen_dmb(enum aarch64_insn_mb_type type);
+u32 aarch64_insn_gen_mrs(enum aarch64_insn_register result,
+			 enum aarch64_insn_system_register sysreg);
 
 s32 aarch64_get_branch_offset(u32 insn);
 u32 aarch64_set_branch_offset(u32 insn, s32 offset);

arch/arm64/lib/insn.c

@@ -1515,3 +1515,14 @@ u32 aarch64_insn_gen_dmb(enum aarch64_insn_mb_type type)
 
 	return insn;
 }
+
+u32 aarch64_insn_gen_mrs(enum aarch64_insn_register result,
+			 enum aarch64_insn_system_register sysreg)
+{
+	u32 insn = aarch64_insn_get_mrs_value();
+
+	insn &= ~GENMASK(19, 0);
+	insn |= sysreg << 5;
+	return aarch64_insn_encode_register(AARCH64_INSN_REGTYPE_RT,
+					    insn, result);
+}

arch/arm64/net/bpf_jit.h

@@ -297,4 +297,12 @@
 #define A64_ADR(Rd, offset) \
 	aarch64_insn_gen_adr(0, offset, Rd, AARCH64_INSN_ADR_TYPE_ADR)
 
+/* MRS */
+#define A64_MRS_TPIDR_EL1(Rt) \
+	aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_TPIDR_EL1)
+#define A64_MRS_TPIDR_EL2(Rt) \
+	aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_TPIDR_EL2)
+#define A64_MRS_SP_EL0(Rt) \
+	aarch64_insn_gen_mrs(Rt, AARCH64_INSN_SYSREG_SP_EL0)
+
 #endif /* _BPF_JIT_H */

arch/arm64/net/bpf_jit_comp.c

@@ -890,6 +890,15 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 			emit(A64_ORR(1, tmp, dst, tmp), ctx);
 			emit(A64_MOV(1, dst, tmp), ctx);
 			break;
+		} else if (insn_is_mov_percpu_addr(insn)) {
+			if (dst != src)
+				emit(A64_MOV(1, dst, src), ctx);
+			if (cpus_have_cap(ARM64_HAS_VIRT_HOST_EXTN))
+				emit(A64_MRS_TPIDR_EL2(tmp), ctx);
+			else
+				emit(A64_MRS_TPIDR_EL1(tmp), ctx);
+			emit(A64_ADD(1, dst, dst, tmp), ctx);
+			break;
 		}
 		switch (insn->off) {
 		case 0:
@@ -1219,6 +1228,21 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 		const u8 r0 = bpf2a64[BPF_REG_0];
 		bool func_addr_fixed;
 		u64 func_addr;
+		u32 cpu_offset;
+
+		/* Implement helper call to bpf_get_smp_processor_id() inline */
+		if (insn->src_reg == 0 && insn->imm == BPF_FUNC_get_smp_processor_id) {
+			cpu_offset = offsetof(struct thread_info, cpu);
+
+			emit(A64_MRS_SP_EL0(tmp), ctx);
+			if (is_lsi_offset(cpu_offset, 2)) {
+				emit(A64_LDR32I(r0, tmp, cpu_offset), ctx);
+			} else {
+				emit_a64_mov_i(1, tmp2, cpu_offset, ctx);
+				emit(A64_LDR32(r0, tmp, tmp2), ctx);
+			}
+			break;
+		}
 
 		ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
 					    &func_addr, &func_addr_fixed);
@@ -2559,6 +2583,21 @@ bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena)
 	return true;
 }
 
+bool bpf_jit_supports_percpu_insn(void)
+{
+	return true;
+}
+
+bool bpf_jit_inlines_helper_call(s32 imm)
+{
+	switch (imm) {
+	case BPF_FUNC_get_smp_processor_id:
+		return true;
+	default:
+		return false;
+	}
+}
+
 void bpf_jit_free(struct bpf_prog *prog)
 {
 	if (prog->jited) {

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 */
@@ -1474,6 +1493,22 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 		bool fixed_addr;
 		u64 addr;
 
+		/* Inline calls to bpf_get_smp_processor_id()
+		 *
+		 * RV_REG_TP holds the address of the current CPU's task_struct and thread_info is
+		 * at offset 0 in task_struct.
+		 * Load cpu from thread_info:
+		 *     Set R0 to ((struct thread_info *)(RV_REG_TP))->cpu
+		 *
+		 * This replicates the implementation of raw_smp_processor_id() on RISCV
+		 */
+		if (insn->src_reg == 0 && insn->imm == BPF_FUNC_get_smp_processor_id) {
+			/* Load current CPU number in R0 */
+			emit_ld(bpf_to_rv_reg(BPF_REG_0, ctx), offsetof(struct thread_info, cpu),
+				RV_REG_TP, ctx);
+			break;
+		}
+
 		mark_call(ctx);
 		ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
 					    &addr, &fixed_addr);
@@ -2038,3 +2073,18 @@ bool bpf_jit_supports_arena(void)
 {
 	return true;
 }
+
+bool bpf_jit_supports_percpu_insn(void)
+{
+	return true;
+}
+
+bool bpf_jit_inlines_helper_call(s32 imm)
+{
+	switch (imm) {
+	case BPF_FUNC_get_smp_processor_id:
+		return true;
+	default:
+		return false;
+	}
+}

include/linux/filter.h

@@ -993,6 +993,7 @@ u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog);
 void bpf_jit_compile(struct bpf_prog *prog);
 bool bpf_jit_needs_zext(void);
+bool bpf_jit_inlines_helper_call(s32 imm);
 bool bpf_jit_supports_subprog_tailcalls(void);
 bool bpf_jit_supports_percpu_insn(void);
 bool bpf_jit_supports_kfunc_call(void);

kernel/bpf/core.c

@@ -2941,6 +2941,17 @@ bool __weak bpf_jit_needs_zext(void)
 	return false;
 }
 
+/* Return true if the JIT inlines the call to the helper corresponding to
+ * the imm.
+ *
+ * The verifier will not patch the insn->imm for the call to the helper if
+ * this returns true.
+ */
+bool __weak bpf_jit_inlines_helper_call(s32 imm)
+{
+	return false;
+}
+
 /* Return TRUE if the JIT backend supports mixing bpf2bpf and tailcalls. */
 bool __weak bpf_jit_supports_subprog_tailcalls(void)
 {

kernel/bpf/verifier.c

@@ -19996,6 +19996,10 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 			goto next_insn;
 		}
 
+		/* Skip inlining the helper call if the JIT does it. */
+		if (bpf_jit_inlines_helper_call(insn->imm))
+			goto next_insn;
+
 		if (insn->imm == BPF_FUNC_get_route_realm)
 			prog->dst_needed = 1;
 		if (insn->imm == BPF_FUNC_get_prandom_u32)