[PATCH bpf-next v2 2/2] bpf, riscv: Remove redundant bpf_flush_icache() after pack allocator finalize

[Puranjay Mohan]

bpf_flush_icache() calls flush_icache_range() to clean the data cache
and invalidate the instruction cache for the JITed code region. However,
since commit 48a8f78c50bd ("bpf, riscv: use prog pack allocator in the
BPF JIT"), this flush is redundant.

bpf_jit_binary_pack_finalize() copies the JITed instructions to the ROX
region via bpf_arch_text_copy() -> patch_text_nosync(), and
patch_text_nosync() already calls flush_icache_range() on the written
range. The subsequent bpf_flush_icache() repeats the same cache
maintenance on an overlapping range.

Remove the redundant bpf_flush_icache() call and its now-unused
definition.

Fixes: 48a8f78c50bd ("bpf, riscv: use prog pack allocator in the BPF JIT")
Acked-by: Song Liu <song@xxxxxxxxxx>
Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx>
---
 arch/riscv/net/bpf_jit.h      | 6 ------
 arch/riscv/net/bpf_jit_core.c | 7 -------
 2 files changed, 13 deletions(-)

diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
index 632ced07bca4..da0271790244 100644
--- a/arch/riscv/net/bpf_jit.h
+++ b/arch/riscv/net/bpf_jit.h
@@ -11,7 +11,6 @@
 
 #include <linux/bpf.h>
 #include <linux/filter.h>
-#include <asm/cacheflush.h>
 
 /* verify runtime detection extension status */
 #define rv_ext_enabled(ext) \
@@ -105,11 +104,6 @@ static inline void bpf_fill_ill_insns(void *area, unsigned int size)
 	memset(area, 0, size);
 }
 
-static inline void bpf_flush_icache(void *start, void *end)
-{
-	flush_icache_range((unsigned long)start, (unsigned long)end);
-}
-
 /* Emit a 4-byte riscv instruction. */
 static inline void emit(const u32 insn, struct rv_jit_context *ctx)
 {
diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index b3581e926436..f7fd4afc3ca3 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -183,13 +183,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 			prog = orig_prog;
 			goto out_offset;
 		}
-		/*
-		 * The instructions have now been copied to the ROX region from
-		 * where they will execute.
-		 * Write any modified data cache blocks out to memory and
-		 * invalidate the corresponding blocks in the instruction cache.
-		 */
-		bpf_flush_icache(jit_data->ro_header, ctx->ro_insns + ctx->ninsns);
 		for (i = 0; i < prog->len; i++)
 			ctx->offset[i] = ninsns_rvoff(ctx->offset[i]);
 		bpf_prog_fill_jited_linfo(prog, ctx->offset);
-- 
2.52.0