bpf, x64: remove bpf_flush_icache

Unlike other archs flush_icache_range() is a noop on x64, therefore
remove the JIT's bpf_flush_icache() altogether since not needed.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Eric Dumazet <edumazet@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/x86/net/bpf_jit_comp.c

@@ -11,10 +11,10 @@
 #include <linux/netdevice.h>
 #include <linux/filter.h>
 #include <linux/if_vlan.h>
-#include <asm/cacheflush.h>
+#include <linux/bpf.h>
+
 #include <asm/set_memory.h>
 #include <asm/nospec-branch.h>
-#include <linux/bpf.h>
 
 /*
  * assembly code in arch/x86/net/bpf_jit.S
@@ -103,16 +103,6 @@ static int bpf_size_to_x86_bytes(int bpf_size)
 #define X86_JLE 0x7E
 #define X86_JG  0x7F
 
-static void bpf_flush_icache(void *start, void *end)
-{
-	mm_segment_t old_fs = get_fs();
-
-	set_fs(KERNEL_DS);
-	smp_wmb();
-	flush_icache_range((unsigned long)start, (unsigned long)end);
-	set_fs(old_fs);
-}
-
 #define CHOOSE_LOAD_FUNC(K, func) \
 	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 
@@ -1266,7 +1256,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 		bpf_jit_dump(prog->len, proglen, pass + 1, image);
 
 	if (image) {
-		bpf_flush_icache(header, image + proglen);
 		if (!prog->is_func || extra_pass) {
 			bpf_jit_binary_lock_ro(header);
 		} else {