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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id b62-v6sm48524496pfa.159.2018.11.19.19.32.19 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 19 Nov 2018 19:32:19 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gOwlu-0001mf-Dp; Mon, 19 Nov 2018 20:32:18 -0700 Date: Mon, 19 Nov 2018 20:32:18 -0700 From: Jason Gunthorpe To: Tom Talpey Cc: "Mora, Jorge" , Chuck Lever , Olga Kornievskaia , linux-rdma , Linux NFS Mailing List Subject: Re: [PATCH v1 4/4] xprtrdma: Plant XID in on-the-wire RDMA offset (FRWR) Message-ID: <20181120033218.GS4890@ziepe.ca> References: <4A94F1A9-96A4-4A2F-8617-AF0E2380D0C1@oracle.com> <9BD3F7C9-96BF-4555-A901-5E82E2CF9E28@oracle.com> <4EE34B64-0BEB-439A-B2A2-D77673D4CF70@oracle.com> <5EA42399-05C2-40D3-A5CA-7B40971AEC33@netapp.com> <20181119224615.GM4890@ziepe.ca> <20181120030916.GQ4890@ziepe.ca> <8fd325fa-290a-6381-80d8-e6ac20acffe8@talpey.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8fd325fa-290a-6381-80d8-e6ac20acffe8@talpey.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Mon, Nov 19, 2018 at 10:25:37PM -0500, Tom Talpey wrote: > Absolutely, but if the offset walks into the high-order invariant bits, > they won't be invariant any longer. It would still work, but it would > defeat the wireshark trick that Chuck wants to play. Sure, OK, if you care about the bits being invarient, and not simply randomized :) > > For many adaptors that means PAGE_SIZE or huge > > page size level alignment.. > > I'm not sure I understand this. The FRWR hides the native page size, by > providing the page frames in the local work request. Their size isn't > known to the protocol. Ah, some HW has limitations in how it can construct a VA. In many implementation the low order bits of the VA must match the offset into the page. If the page is 4K that is 12 bits, if it is 2M that is 21 bits.. So there should be restrictions on what start VA can be assigned to a FRWR. Jason