[PATCH bpf-next] bpf, arm64: Add support for lse atomics in bpf_arena

[Puranjay Mohan]

Puranjay Mohan <puranjay at kernel.org> writes:

> When LSE atomics are available, BPF atomic instructions are implemented
> as single ARM64 atomic instructions, therefore it is easy to enable
> these in bpf_arena using the currently available exception handling
> setup.
>
> LL_SC atomics use loops and therefore would need more work to enable in
> bpf_arena.
>
> Enable LSE atomics based instructions in bpf_arena and use the
> bpf_jit_supports_insn() callback to reject atomics in bpf_arena if LSE
> atomics are not available.
>
> All atomics and arena_atomics selftests are passing:
>
>   [root at ip-172-31-2-216 bpf]# ./test_progs -a atomics,arena_atomics
>   #3/1     arena_atomics/add:OK
>   #3/2     arena_atomics/sub:OK
>   #3/3     arena_atomics/and:OK
>   #3/4     arena_atomics/or:OK
>   #3/5     arena_atomics/xor:OK
>   #3/6     arena_atomics/cmpxchg:OK
>   #3/7     arena_atomics/xchg:OK
>   #3       arena_atomics:OK
>   #10/1    atomics/add:OK
>   #10/2    atomics/sub:OK
>   #10/3    atomics/and:OK
>   #10/4    atomics/or:OK
>   #10/5    atomics/xor:OK
>   #10/6    atomics/cmpxchg:OK
>   #10/7    atomics/xchg:OK
>   #10      atomics:OK
>   Summary: 2/14 PASSED, 0 SKIPPED, 0 FAILED

Gentle ping about this,

Thanks,
Puranjay