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Wed, 29 Mar 2023 14:46:10 -0700 (PDT) X-Google-Smtp-Source: AKy350ZGQUYQJeTXwnRV15le8g2e5F6QxBAZ5bivkYpLnhuEBXno6vpJg9RQt0C5heMRA6NQh8z/2A== X-Received: by 2002:a17:907:7f86:b0:926:9c33:ea4 with SMTP id qk6-20020a1709077f8600b009269c330ea4mr23062308ejc.27.1680126369951; Wed, 29 Mar 2023 14:46:09 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id z26-20020a17090674da00b009310d4dece9sm16869157ejl.62.2023.03.29.14.46.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Mar 2023 14:46:09 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 974C8A22B54; Wed, 29 Mar 2023 23:46:08 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Jesper Dangaard Brouer , bpf@vger.kernel.org, Stanislav Fomichev Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, martin.lau@kernel.org, ast@kernel.org, daniel@iogearbox.net, alexandr.lobakin@intel.com, larysa.zaremba@intel.com, xdp-hints@xdp-project.net, anthony.l.nguyen@intel.com, yoong.siang.song@intel.com, boon.leong.ong@intel.com, intel-wired-lan@lists.osuosl.org, pabeni@redhat.com, jesse.brandeburg@intel.com, kuba@kernel.org, edumazet@google.com, john.fastabend@gmail.com, hawk@kernel.org, davem@davemloft.net Subject: Re: [xdp-hints] [PATCH bpf RFC-V2 1/5] xdp: rss hash types representation In-Reply-To: <168010734324.3039990.16454026957159811204.stgit@firesoul> References: <168010726310.3039990.2753040700813178259.stgit@firesoul> <168010734324.3039990.16454026957159811204.stgit@firesoul> X-Clacks-Overhead: GNU Terry Pratchett Date: Wed, 29 Mar 2023 23:46:08 +0200 Message-ID: <87355nnsdb.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jesper Dangaard Brouer writes: > diff --git a/net/core/xdp.c b/net/core/xdp.c > index 7133017bcd74..81d41df30695 100644 > --- a/net/core/xdp.c > +++ b/net/core/xdp.c > @@ -721,12 +721,14 @@ __bpf_kfunc int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx, u64 *tim > * @hash: Return value pointer. > * > * Return: > - * * Returns 0 on success or ``-errno`` on error. > + * * Returns (positive) RSS hash **type** on success or ``-errno`` on error. This change is going to break any BPF program that does: if (!bpf_xdp_metadata_rx_hash(ctx, &hash)) /* do something with hash */ so I think adding a second argument is better; that way, at least breakage will be explicit instead of being a hidden change in semantics (and the CO-RE style checking for kfuncs Alexei introduced should trigger correctly). But really, what we should do anyway is merge this during the -rc phase to minimise any breakage :) -Toke