bpf: notify offload JITs about optimizations

Let offload JITs know when instructions are replaced and optimized
out, so they can update their state appropriately.  The optimizations
are best effort, if JIT returns an error from any callback verifier
will stop notifying it as state may now be out of sync, but the
verifier continues making progress.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

4 files changed, 53 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e734f163bd0b..3851529062ec 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -268,9 +268,15 @@ struct bpf_verifier_ops {
 };
 
 struct bpf_prog_offload_ops {
+	/* verifier basic callbacks */
 	int (*insn_hook)(struct bpf_verifier_env *env,
 			 int insn_idx, int prev_insn_idx);
 	int (*finalize)(struct bpf_verifier_env *env);
+	/* verifier optimization callbacks (called after .finalize) */
+	int (*replace_insn)(struct bpf_verifier_env *env, u32 off,
+			    struct bpf_insn *insn);
+	int (*remove_insns)(struct bpf_verifier_env *env, u32 off, u32 cnt);
+	/* program management callbacks */
 	int (*prepare)(struct bpf_prog *prog);
 	int (*translate)(struct bpf_prog *prog);
 	void (*destroy)(struct bpf_prog *prog);
@@ -283,6 +289,7 @@ struct bpf_prog_offload {
 	void			*dev_priv;
 	struct list_head	offloads;
 	bool			dev_state;
+	bool			opt_failed;
 	void			*jited_image;
 	u32			jited_len;
 };
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index f3ae00ee5516..0620e418dde5 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -266,5 +266,10 @@ int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
 				 int insn_idx, int prev_insn_idx);
 int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
+void
+bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
+			      struct bpf_insn *insn);
+void
+bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
 #endif /* _LINUX_BPF_VERIFIER_H */
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 54cf2b9c44a4..39dba8c90331 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -173,6 +173,41 @@ int bpf_prog_offload_finalize(struct bpf_verifier_env *env)
 	return ret;
 }
 
+void
+bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
+			      struct bpf_insn *insn)
+{
+	const struct bpf_prog_offload_ops *ops;
+	struct bpf_prog_offload *offload;
+	int ret = -EOPNOTSUPP;
+
+	down_read(&bpf_devs_lock);
+	offload = env->prog->aux->offload;
+	if (offload) {
+		ops = offload->offdev->ops;
+		if (!offload->opt_failed && ops->replace_insn)
+			ret = ops->replace_insn(env, off, insn);
+		offload->opt_failed |= ret;
+	}
+	up_read(&bpf_devs_lock);
+}
+
+void
+bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
+{
+	struct bpf_prog_offload *offload;
+	int ret = -EOPNOTSUPP;
+
+	down_read(&bpf_devs_lock);
+	offload = env->prog->aux->offload;
+	if (offload) {
+		if (!offload->opt_failed && offload->offdev->ops->remove_insns)
+			ret = offload->offdev->ops->remove_insns(env, off, cnt);
+		offload->opt_failed |= ret;
+	}
+	up_read(&bpf_devs_lock);
+}
+
 static void __bpf_prog_offload_destroy(struct bpf_prog *prog)
 {
 	struct bpf_prog_offload *offload = prog->aux->offload;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f2c49b4235df..8cfe39ef770f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6558,6 +6558,9 @@ static int verifier_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
 	unsigned int orig_prog_len = env->prog->len;
 	int err;
 
+	if (bpf_prog_is_dev_bound(env->prog->aux))
+		bpf_prog_offload_remove_insns(env, off, cnt);
+
 	err = bpf_remove_insns(env->prog, off, cnt);
 	if (err)
 		return err;
@@ -6632,6 +6635,9 @@ static void opt_hard_wire_dead_code_branches(struct bpf_verifier_env *env)
 		else
 			continue;
 
+		if (bpf_prog_is_dev_bound(env->prog->aux))
+			bpf_prog_offload_replace_insn(env, i, &ja);
+
 		memcpy(insn, &ja, sizeof(ja));
 	}
 }