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Date: Mon, 22 Mar 2021 16:37:53 +0000 (UTC)
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, kafai@...com,
songliubraving@...com, yhs@...com, john.fastabend@...il.com,
kpsingh@...omium.org, naveen.n.rao@...ux.ibm.com,
sandipan@...ux.ibm.com
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v2 8/8] powerpc/bpf: Reallocate BPF registers to volatile
registers when possible on PPC32
When the BPF routine doesn't call any function, the non volatile
registers can be reallocated to volatile registers in order to
avoid having to save them/restore on the stack.
Before this patch, the test #359 ADD default X is:
0: 7c 64 1b 78 mr r4,r3
4: 38 60 00 00 li r3,0
8: 94 21 ff b0 stwu r1,-80(r1)
c: 60 00 00 00 nop
10: 92 e1 00 2c stw r23,44(r1)
14: 93 01 00 30 stw r24,48(r1)
18: 93 21 00 34 stw r25,52(r1)
1c: 93 41 00 38 stw r26,56(r1)
20: 39 80 00 00 li r12,0
24: 39 60 00 00 li r11,0
28: 3b 40 00 00 li r26,0
2c: 3b 20 00 00 li r25,0
30: 7c 98 23 78 mr r24,r4
34: 7c 77 1b 78 mr r23,r3
38: 39 80 00 42 li r12,66
3c: 39 60 00 00 li r11,0
40: 7d 8c d2 14 add r12,r12,r26
44: 39 60 00 00 li r11,0
48: 7d 83 63 78 mr r3,r12
4c: 82 e1 00 2c lwz r23,44(r1)
50: 83 01 00 30 lwz r24,48(r1)
54: 83 21 00 34 lwz r25,52(r1)
58: 83 41 00 38 lwz r26,56(r1)
5c: 38 21 00 50 addi r1,r1,80
60: 4e 80 00 20 blr
After this patch, the same test has become:
0: 7c 64 1b 78 mr r4,r3
4: 38 60 00 00 li r3,0
8: 94 21 ff b0 stwu r1,-80(r1)
c: 60 00 00 00 nop
10: 39 80 00 00 li r12,0
14: 39 60 00 00 li r11,0
18: 39 00 00 00 li r8,0
1c: 38 e0 00 00 li r7,0
20: 7c 86 23 78 mr r6,r4
24: 7c 65 1b 78 mr r5,r3
28: 39 80 00 42 li r12,66
2c: 39 60 00 00 li r11,0
30: 7d 8c 42 14 add r12,r12,r8
34: 39 60 00 00 li r11,0
38: 7d 83 63 78 mr r3,r12
3c: 38 21 00 50 addi r1,r1,80
40: 4e 80 00 20 blr
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
arch/powerpc/net/bpf_jit.h | 16 ++++++++++++++++
arch/powerpc/net/bpf_jit64.h | 2 +-
arch/powerpc/net/bpf_jit_comp.c | 2 ++
arch/powerpc/net/bpf_jit_comp32.c | 30 ++++++++++++++++++++++++++++--
arch/powerpc/net/bpf_jit_comp64.c | 4 ++++
5 files changed, 51 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index a45b8266355d..776abef4d2a0 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -116,6 +116,15 @@ static inline bool is_nearbranch(int offset)
#define SEEN_STACK 0x40000000 /* uses BPF stack */
#define SEEN_TAILCALL 0x80000000 /* uses tail calls */
+#define SEEN_VREG_MASK 0x1ff80000 /* Volatile registers r3-r12 */
+#define SEEN_NVREG_MASK 0x0003ffff /* Non volatile registers r14-r31 */
+
+#ifdef CONFIG_PPC64
+extern const int b2p[MAX_BPF_JIT_REG + 2];
+#else
+extern const int b2p[MAX_BPF_JIT_REG + 1];
+#endif
+
struct codegen_context {
/*
* This is used to track register usage as well
@@ -129,6 +138,7 @@ struct codegen_context {
unsigned int seen;
unsigned int idx;
unsigned int stack_size;
+ int b2p[ARRAY_SIZE(b2p)];
};
static inline void bpf_flush_icache(void *start, void *end)
@@ -147,11 +157,17 @@ static inline void bpf_set_seen_register(struct codegen_context *ctx, int i)
ctx->seen |= 1 << (31 - i);
}
+static inline void bpf_clear_seen_register(struct codegen_context *ctx, int i)
+{
+ ctx->seen &= ~(1 << (31 - i));
+}
+
void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 func);
int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
u32 *addrs, bool extra_pass);
void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx);
void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx);
+void bpf_jit_realloc_regs(struct codegen_context *ctx);
#endif
diff --git a/arch/powerpc/net/bpf_jit64.h b/arch/powerpc/net/bpf_jit64.h
index b05f2e67bba1..7b713edfa7e2 100644
--- a/arch/powerpc/net/bpf_jit64.h
+++ b/arch/powerpc/net/bpf_jit64.h
@@ -39,7 +39,7 @@
#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)
/* BPF to ppc register mappings */
-static const int b2p[] = {
+const int b2p[MAX_BPF_JIT_REG + 2] = {
/* function return value */
[BPF_REG_0] = 8,
/* function arguments */
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index efac89964873..798ac4350a82 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -143,6 +143,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
}
memset(&cgctx, 0, sizeof(struct codegen_context));
+ memcpy(cgctx.b2p, b2p, sizeof(cgctx.b2p));
/* Make sure that the stack is quadword aligned. */
cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
@@ -167,6 +168,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
}
}
+ bpf_jit_realloc_regs(&cgctx);
/*
* Pretend to build prologue, given the features we've seen. This will
* update ctgtx.idx as it pretends to output instructions, then we can
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index 29ce802d7534..003843273b43 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -37,7 +37,7 @@
#define TMP_REG (MAX_BPF_JIT_REG + 0)
/* BPF to ppc register mappings */
-static const int b2p[] = {
+const int b2p[MAX_BPF_JIT_REG + 1] = {
/* function return value */
[BPF_REG_0] = 12,
/* function arguments */
@@ -60,7 +60,7 @@ static const int b2p[] = {
static int bpf_to_ppc(struct codegen_context *ctx, int reg)
{
- return b2p[reg];
+ return ctx->b2p[reg];
}
/* PPC NVR range -- update this if we ever use NVRs below r17 */
@@ -77,6 +77,32 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)
return BPF_PPC_STACKFRAME(ctx) - 4;
}
+void bpf_jit_realloc_regs(struct codegen_context *ctx)
+{
+ if (ctx->seen & SEEN_FUNC)
+ return;
+
+ while (ctx->seen & SEEN_NVREG_MASK &&
+ (ctx->seen & SEEN_VREG_MASK) != SEEN_VREG_MASK) {
+ int old = 32 - fls(ctx->seen & (SEEN_NVREG_MASK & 0xaaaaaaab));
+ int new = 32 - fls(~ctx->seen & (SEEN_VREG_MASK & 0xaaaaaaaa));
+ int i;
+
+ for (i = BPF_REG_0; i <= TMP_REG; i++) {
+ if (ctx->b2p[i] != old)
+ continue;
+ ctx->b2p[i] = new;
+ bpf_set_seen_register(ctx, new);
+ bpf_clear_seen_register(ctx, old);
+ if (i != TMP_REG) {
+ bpf_set_seen_register(ctx, new - 1);
+ bpf_clear_seen_register(ctx, old - 1);
+ }
+ break;
+ }
+ }
+}
+
void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
int i;
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 8a1f9fb00e78..57a8c1153851 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -64,6 +64,10 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)
BUG();
}
+void bpf_jit_realloc_regs(struct codegen_context *ctx)
+{
+}
+
void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
int i;
--
2.25.0
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