[PATCH bpf-next v2 0/2] bpf, arm64/riscv: Remove redundant icache flush after pack allocator finalize

[PATCH bpf-next v2 0/2] bpf, arm64/riscv: Remove redundant icache flush after pack allocator finalize

[Puranjay Mohan]

Changelog:
v1: https://lore.kernel.org/all/20260413123256.3296452-1-puranjay@kernel.org/
Changes in v2:
- Remove "#include <asm/cacheflush.h>" as it is not needed now.
- Add Acked-by: Song Liu <song@kernel.org>

When the BPF prog pack allocator was added for arm64 and riscv, the
existing bpf_flush_icache() calls were retained after
bpf_jit_binary_pack_finalize(). However, the finalize path copies the
JITed code via architecture text patching routines (__text_poke on arm64,
patch_text_nosync on riscv) that already perform a full
flush_icache_range() internally. The subsequent bpf_flush_icache()
repeats the same cache maintenance on the same range.

Remove the redundant flush and the now-unused bpf_flush_icache()
definitions on both architectures.

Puranjay Mohan (2):
  bpf, arm64: Remove redundant bpf_flush_icache() after pack allocator
    finalize
  bpf, riscv: Remove redundant bpf_flush_icache() after pack allocator
    finalize

 arch/arm64/net/bpf_jit_comp.c | 12 ------------
 arch/riscv/net/bpf_jit.h      |  6 ------
 arch/riscv/net/bpf_jit_core.c |  7 -------
 3 files changed, 25 deletions(-)


base-commit: 71b500afd2f7336f5b6c6026f2af546fc079be26
-- 
2.52.0


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[PATCH bpf-next v2 1/2] bpf, arm64: 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 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory
management"), this flush is redundant.

bpf_jit_binary_pack_finalize() copies the JITed instructions to the ROX
region via bpf_arch_text_copy() -> aarch64_insn_copy() -> __text_poke(),
and __text_poke() already calls flush_icache_range() on the written
range. The subsequent bpf_flush_icache() repeats the same cache
maintenance on an overlapping range, including an unnecessary second
synchronous IPI to all CPUs via kick_all_cpus_sync().

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

Fixes: 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory management")
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
 arch/arm64/net/bpf_jit_comp.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index adf84962d579..7417d24a5b6f 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -18,7 +18,6 @@
 
 #include <asm/asm-extable.h>
 #include <asm/byteorder.h>
-#include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
@@ -1961,11 +1960,6 @@ static int validate_ctx(struct jit_ctx *ctx)
 	return 0;
 }
 
-static inline void bpf_flush_icache(void *start, void *end)
-{
-	flush_icache_range((unsigned long)start, (unsigned long)end);
-}
-
 static void priv_stack_init_guard(void __percpu *priv_stack_ptr, int alloc_size)
 {
 	int cpu, underflow_idx = (alloc_size - PRIV_STACK_GUARD_SZ) >> 3;
@@ -2204,12 +2198,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 			prog = orig_prog;
 			goto out_off;
 		}
-		/*
-		 * The instructions have now been copied to the ROX region from
-		 * where they will execute. Now the data cache has to be cleaned to
-		 * the PoU and the I-cache has to be invalidated for the VAs.
-		 */
-		bpf_flush_icache(ro_header, ctx.ro_image + ctx.idx);
 	} else {
 		jit_data->ctx = ctx;
 		jit_data->ro_image = ro_image_ptr;
-- 
2.52.0


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Re: [PATCH bpf-next v2 1/2] bpf, arm64: Remove redundant bpf_flush_icache() after pack allocator finalize

[Xu Kuohai]

On 4/14/2026 3:11 AM, Puranjay Mohan wrote:
> 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 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory
> management"), this flush is redundant.
> 
> bpf_jit_binary_pack_finalize() copies the JITed instructions to the ROX
> region via bpf_arch_text_copy() -> aarch64_insn_copy() -> __text_poke(),
> and __text_poke() already calls flush_icache_range() on the written
> range. The subsequent bpf_flush_icache() repeats the same cache
> maintenance on an overlapping range, including an unnecessary second
> synchronous IPI to all CPUs via kick_all_cpus_sync().
>

So icache is flushed twice: once per instruction and again after all
instructions are copied. I think it's better to remove the per-instruction
flush and retain the single final flush to avoid repeating flush overhead
for each instruction.

> Remove the redundant bpf_flush_icache() call and its now-unused
> definition.
> 
> Fixes: 1dad391daef1 ("bpf, arm64: use bpf_prog_pack for memory management")
> Acked-by: Song Liu <song@kernel.org>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
>   arch/arm64/net/bpf_jit_comp.c | 12 ------------
>   1 file changed, 12 deletions(-)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index adf84962d579..7417d24a5b6f 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -18,7 +18,6 @@
>   
>   #include <asm/asm-extable.h>
>   #include <asm/byteorder.h>
> -#include <asm/cacheflush.h>
>   #include <asm/cpufeature.h>
>   #include <asm/debug-monitors.h>
>   #include <asm/insn.h>
> @@ -1961,11 +1960,6 @@ static int validate_ctx(struct jit_ctx *ctx)
>   	return 0;
>   }
>   
> -static inline void bpf_flush_icache(void *start, void *end)
> -{
> -	flush_icache_range((unsigned long)start, (unsigned long)end);
> -}
> -
>   static void priv_stack_init_guard(void __percpu *priv_stack_ptr, int alloc_size)
>   {
>   	int cpu, underflow_idx = (alloc_size - PRIV_STACK_GUARD_SZ) >> 3;
> @@ -2204,12 +2198,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>   			prog = orig_prog;
>   			goto out_off;
>   		}
> -		/*
> -		 * The instructions have now been copied to the ROX region from
> -		 * where they will execute. Now the data cache has to be cleaned to
> -		 * the PoU and the I-cache has to be invalidated for the VAs.
> -		 */
> -		bpf_flush_icache(ro_header, ctx.ro_image + ctx.idx);
>   	} else {
>   		jit_data->ctx = ctx;
>   		jit_data->ro_image = ro_image_ptr;


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[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@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
---
 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


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

[Pu Lehui]

On 2026/4/14 3:11, Puranjay Mohan wrote:
> 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@kernel.org>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
> ---
>   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);

Reviewed-by: Pu Lehui <pulehui@huawei.com>

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