Re: [PATCH 0/5] Atomics support for eBPF on powerpc

[Michael Ellerman <mpe@ellerman.id.au>]

Daniel Borkmann <daniel@iogearbox.net> writes:
> On 5/12/22 9:45 AM, Hari Bathini wrote:
>> This patchset adds atomic operations to the eBPF instruction set on
>> powerpc. The instructions that are added here can be summarised with
>> this list of kernel operations for ppc64:
>> 
>> * atomic[64]_[fetch_]add
>> * atomic[64]_[fetch_]and
>> * atomic[64]_[fetch_]or
>> * atomic[64]_[fetch_]xor
>> * atomic[64]_xchg
>> * atomic[64]_cmpxchg
>> 
>> and this list of kernel operations for ppc32:
>> 
>> * atomic_[fetch_]add
>> * atomic_[fetch_]and
>> * atomic_[fetch_]or
>> * atomic_[fetch_]xor
>> * atomic_xchg
>> * atomic_cmpxchg
>> 
>> The following are left out of scope for this effort:
>> 
>> * 64 bit operations on ppc32.
>> * Explicit memory barriers, 16 and 8 bit operations on both ppc32
>>    & ppc64.
>> 
>> The first patch adds support for bitwsie atomic operations on ppc64.
>> The next patch adds fetch variant support for these instructions. The
>> third patch adds support for xchg and cmpxchg atomic operations on
>> ppc64. Patch #4 adds support for 32-bit atomic bitwise operations on
>> ppc32. patch #5 adds support for xchg and cmpxchg atomic operations
>> on ppc32.
>
> Thanks for adding these, Hari! I presume they'll get routed via Michael,
> right?

Yeah I'm happy to take them if they are OK by you.

I do wonder if the BPF jit code should eventually move out of arch/, but
that's a discussion for another day.

> One thing that may be worth adding to the commit log as well is
> the test result from test_bpf.ko given it has an extensive suite around
> atomics useful for testing corner cases in JITs.

Yes please, test results make me feel much better about merging things :)

cheers