From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44B571D5147; Tue, 28 Oct 2025 12:31:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761654668; cv=none; b=WQvYjKB4+7G+zt68kqbMd07gM6Vxc1W5792Ih3bzfYn0umJIF4MQI6clBv4MhPEoVvi9GJ8otmOmUNY3NlrAYf4tRifdnO+WPAZ3VPPYYYldIhIigoYSu3LKXDPN4ClLTUv9twZX3qvmIkNmKeHTG/TIprOA9FbxtMInYNYrnbY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761654668; c=relaxed/simple; bh=bp3dDj7WuCgUaozIZmBCOLT7S6dPjUy422kqru/krws=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gbbIPw4B/Ur6oOx/5IKKXZ0jr/nB8+RIBo6TKHxm/LWwAWsDnB6DvkZq+pzcUedHZaSjOVMIPWoizuRsb7xhkSPWKZkrCWQo9USXjOG+PSUDKgAKYOD1a0EWBDiqShvySQ789bHFmGR/07Z7KQtYwJtCfL/KFkadpp47MATrVqo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MqhYqjzw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MqhYqjzw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E6128C4CEE7; Tue, 28 Oct 2025 12:31:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761654666; bh=bp3dDj7WuCgUaozIZmBCOLT7S6dPjUy422kqru/krws=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MqhYqjzwPAqrvZy+5lthpH7b+sHTqLCG3GPCT/sK1zBLYshcGv57uRgmwywUHvEdX 5sammRMOG23AlLMM3m0AoRRBpwJzKvJTbbRvUZisAp5DIbueJkQihcWM2VNHu57inM Nwe3yv15/0dAqcafexYvDx5JQ0E8K2/tGy3Zq4ms5TpUD+f3cmWp4yq4fRl8JEftc2 K38c+XOVnKgfP2WIR2lL6T8MwvZOFhggFN89K/3iqug0c4Cbr8fxrVlyITjJwc2Df3 8gnyzGdDeL26rlulVbiCkl+WSVo8gy8Axggq0M4PIa29tIOI1Db6pk6n1GJeX+llBf leMHOZuTLRwLw== Date: Tue, 28 Oct 2025 14:31:01 +0200 From: Leon Romanovsky To: "D. Wythe" Cc: mjambigi@linux.ibm.com, wenjia@linux.ibm.com, wintera@linux.ibm.com, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com, guwen@linux.alibaba.com, kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, sidraya@linux.ibm.com, jaka@linux.ibm.com Subject: Re: [PATCH net-next v2] net/smc: add full IPv6 support for SMC Message-ID: <20251028123101.GR12554@unreal> References: <20251022032309.66386-1-alibuda@linux.alibaba.com> <20251027134227.GL12554@unreal> <20251028095450.GA38488@j66a10360.sqa.eu95> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251028095450.GA38488@j66a10360.sqa.eu95> On Tue, Oct 28, 2025 at 05:54:50PM +0800, D. Wythe wrote: > On Mon, Oct 27, 2025 at 03:42:27PM +0200, Leon Romanovsky wrote: > > On Wed, Oct 22, 2025 at 11:23:09AM +0800, D. Wythe wrote: > > > The current SMC implementation is IPv4-centric. While it contains a > > > workaround for IPv4-mapped IPv6 addresses, it lacks a functional path > > > for native IPv6, preventing its use in modern dual-stack or IPv6-only > > > networks. > > > > > > This patch introduces full, native IPv6 support by refactoring the > > > address handling mechanism to be IP-version agnostic, which is > > > achieved by: > > > > > > - Introducing a generic `struct smc_ipaddr` to abstract IP addresses. > > > - Implementing an IPv6-specific route lookup function. > > > - Extend GID matching logic for both IPv4 and IPv6 addresses > > > > > > With these changes, SMC can now discover RDMA devices and establish > > > connections over both native IPv4 and IPv6 networks. > > > > Why can't you use rdma-cm in-kernel API like any other in-kernel RDMA consumers? > > > > Thanks > > > > > > > Hi Leon, > > Regarding RDMA-CM, I’m not sure if I’ve fully grasped your point, but > based on my current understanding, I believe SMC cannot use RDMA-CM. > There are a few reasons for this: > > Firstly, SMC is designed to work not only with RDMA devices but also > needs to negotiate with DIBS(DIRECT INTERNAL BUFFER SHARING) devices. This > means we must support scenarios where no RDMA device is present. > Therefore, we require a round of out-of-band negotiation regardless of > the final device choice. In this context, even if we ultimately select > an RDMA device, using rdma-cm to establish the connection would be > redundant. Ahh, yes, I always failed to remember this. Thanks > > Additionally, SMC requires multiplexing multiple connections over a > single QP. We need to decide during the out-of-band negotiation which > specific QP to reuse for the connection. From what I know, rdma-cm does > not seem to offer this capability either. > > Best regards, > D. Wythe >