Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760165AbXLMIbQ (ORCPT ); Thu, 13 Dec 2007 03:31:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754253AbXLMIbA (ORCPT ); Thu, 13 Dec 2007 03:31:00 -0500 Received: from fwil.voltaire.com ([193.47.165.2]:16927 "EHLO exil.voltaire.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753026AbXLMIbA (ORCPT ); Thu, 13 Dec 2007 03:31:00 -0500 Message-ID: <4760EDC0.5020703@voltaire.com> Date: Thu, 13 Dec 2007 10:30:56 +0200 From: Or Gerlitz User-Agent: Thunderbird 1.4.1 (Windows/20051006) MIME-Version: 1.0 To: Roland Dreier CC: Joachim Fenkes , Arnd Bergmann , LKML , linuxppc-dev@ozlabs.org, Christoph Raisch , OF-General , Stefan Roscher Subject: Re: [ewg] Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5 References: <475FD0A1.3090304@voltaire.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 13 Dec 2007 08:30:57.0761 (UTC) FILETIME=[7C109510:01C83D62] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1372 Lines: 31 Roland Dreier wrote: > I think the right fix for iSER would be to make iSER work even for > devices that don't support FMRs. For example cxgb3 doesn't implement > FMRs so if anyone ever updates iSER to work on iWARP and not just IB, > then this is something that has to be tackled anyway. Then ehca could > just get rid of the FMR support it has. OK, The iSER design took into account the case of many initiators running on strong/modern machines talking to possibly lightweight embedded target for which the processing cost per I/O at the target side should be minimized, that is at most --one-- RDMA operation should be issued by the target to serve an I/O request. For that end, iSER works with one descriptor (called stag in iWARP and rkey in IB) per I/O direction sent from the initiator to the target and hence can't work without some sort of FMR implementation. The current implementation of the open iscsi initiator makes sure to issue commands in thread (sleepable) context, see iscsi_xmitworker and references to it in drivers/scsi/libiscsi.c , so this keeps ehca users safe for the time being. Or. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/