From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [RFC net-next PATCH 4/5] net: new XDP feature for reading HW rxhash from drivers Date: Fri, 19 May 2017 21:13:14 -0700 Message-ID: <20170519211314.5a14a402@cakuba.netronome.com> References: <149512205297.14733.15729847433404265933.stgit@firesoul> <149512210827.14733.13997041998775151648.stgit@firesoul> <20170520030750.c2b55oqdms5n764c@ast-mbp> <20170519202147.3c6bda7f@cakuba.netronome.com> <20170520033358.hjz7ocy2fupwplym@ast-mbp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Jesper Dangaard Brouer , Daniel Borkmann , netdev@vger.kernel.org To: Alexei Starovoitov Return-path: Received: from mx4.wp.pl ([212.77.101.11]:13972 "EHLO mx4.wp.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751153AbdETENi (ORCPT ); Sat, 20 May 2017 00:13:38 -0400 In-Reply-To: <20170520033358.hjz7ocy2fupwplym@ast-mbp> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 19 May 2017 20:34:00 -0700, Alexei Starovoitov wrote: > On Fri, May 19, 2017 at 08:21:47PM -0700, Jakub Kicinski wrote: > > On Fri, 19 May 2017 20:07:52 -0700, Alexei Starovoitov wrote: > > > How about exposing 'struct mlx5_cqe64 *' to XDP programs as-is? > > > We can make sure that XDP program does read only access into it and > > > it will see cqe->rss_hash_result, cqe->rss_hash_type and everything else > > > in there, but this will not be uapi and it will be pretty obvious > > > to program authors that their programs are vendor specific. > > > 'not uapi' here means that mellanox is free to change their HW descriptor > > > and its contents as they wish. > > > > Hm.. Would that mean we have to teach the verifier about all possible > > drivers and their metadata structures (i.e. sizes thereof). And add an > > UAPI enum of known drivers? > > why? no uapi other than a pointer to this hw rx descriptor. > Different sizeof(hw_rx_descriptor) is not a problem. > We deal with it already in tracing. All tracepoints have different > sizeof(*ctx), yet the safety is preserved. Ack, quick read of tracing code reveals this indeed should work.