From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: net/smc and the RDMA core Date: Thu, 4 May 2017 11:43:50 +0300 Message-ID: <1b79048f-4495-3840-e7a6-d4fa5a8dfb57@grimberg.me> References: <20170501163311.GA22209@lst.de> <1493750358.2552.13.camel@sandisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1493750358.2552.13.camel-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche , "hch-jcswGhMUV9g@public.gmane.org" , "davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org" , "ubraun-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org" Cc: "netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org >> if you can point out specific issues, we will be happy to work with you >> to get them addressed! > > Hello Ursula, > > My list of issues that I would like to see addressed can be found below. Doug, > Christoph and others may have additional inputs. The issues that have not yet > been mentioned in other e-mails are: > - The SMC driver only supports one RDMA transport type (RoCE v1) but > none of the other RDMA transport types (RoCE v2, IB and iWARP). New > RDMA drivers should support all RDMA transport types transparently. > The traditional approach to support multiple RDMA transport types is > by using the RDMA/CM to establish connections. > - The implementation of the SMC driver only supports RoCEv1. This is > a very unfortunate choice because: > - RoCEv1 is not routable and hence is limited to a single Ethernet > broadcast domain. > - RoCEv1 packets escape a whole bunch of mechanisms that only work > for IP packets. Firewalls pass all RoCEv1 packets and switches > do not restrict RoCEv1 packets to a single VLAN. This means that > if the network configuration is changed after an SMC connection > has been set up such that IP communication between the endpoints > of an SMC connection is blocked that the SMC RoCEv1 packets will > not be blocked by the network equipment of which the configuration > has just been changed. > - As already mentioned by Christoph, the SMC implementation uses RDMA > calls that probably will be deprecated soon (ib_create_cq()) and > should use the RDMA R/W API instead of building sge lists itself. I would also suggest that you stop exposing the DMA MR for remote access (at least by default) and use a proper reg_mr operations with a limited lifetime on a properly sized buffer. Also, the cq polling code looks completely wrong, you should really use the RDMA CQ API. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html