Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932819AbXLMVAR (ORCPT ); Thu, 13 Dec 2007 16:00:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763623AbXLMU74 (ORCPT ); Thu, 13 Dec 2007 15:59:56 -0500 Received: from mtagate3.de.ibm.com ([195.212.29.152]:2958 "EHLO mtagate3.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763384AbXLMU7y (ORCPT ); Thu, 13 Dec 2007 15:59:54 -0500 In-Reply-To: <469958e00712131122s661dd970ud359389e1c6637d4@mail.gmail.com> To: "Caitlin Bestler" Cc: "Arnd Bergmann" , caitlin.bestler@gmail.com, OF-General , LKML , linuxppc-dev@ozlabs.org, "Or Gerlitz" , "Roland Dreier" , Stefan Roscher MIME-Version: 1.0 Subject: Re: [ofa-general] Re: [ewg] Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5 X-Mailer: Lotus Notes Release 7.0 HF277 June 21, 2006 From: Joachim Fenkes Message-ID: Date: Thu, 13 Dec 2007 21:59:50 +0100 X-MIMETrack: Serialize by Router on D12ML064/12/M/IBM(Release 7.0.2HF71 | November 3, 2006) at 13/12/2007 21:59:51, Serialize complete at 13/12/2007 21:59:51 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1477 Lines: 32 caitlin.bestler@gmail.com wrote on 13.12.2007 20:22:49: > On Dec 13, 2007 12:30 AM, Or Gerlitz wrote: > > 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. > I agree, *some* form of FMR support is important for iSER (and probably > for NFS over RDMA as well). Rather than adding a crippled NO FMR > mode it would make more sense to add support for FMR Work Requests. > I'm not certain what, if any, impact that would have on the Power5 problem, > but that's certainly a cleaner path for iWARP. Well, FMR WRs wouldn't change the eHCA issue -- the driver would have to make an hCall in any case, and the architecture says that the hCalls used in this scenario might return H_LONG_BUSY, causing the driver to sleep. No way around that. Because of this, eHCA's FMRs are actually standard MRs with a different API. If, as Or said, the iSCSI initiator issues commands in sleepable context anyway, nothing would be lost by using standard MRs as a fallback solution if FMRs aren't available, would it? J. -- 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/