From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE936C43381 for ; Fri, 1 Mar 2019 00:30:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 972212087E for ; Fri, 1 Mar 2019 00:30:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551400215; bh=luCTbSmawhSdnFbAJtXA9GGBlXlyIXKPu/7OPefZcFU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=x3A+mdKwpmfAHGzv2Lv0548TmJlb4KVkIF/PTEW8aovCVtpxoG++8x8aLEwVj43k+ jSd3rFANBgm9OL7G5dNZejnEH5C5Np1mHIYw6+7o7GFbi7To6F9XYQj54Oha9g/oLX ovmVyxPPfDR39uPP/mG9fAiqUGAoghhAb8/oKZiE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732704AbfCAAaO (ORCPT ); Thu, 28 Feb 2019 19:30:14 -0500 Received: from mga05.intel.com ([192.55.52.43]:7400 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726678AbfCAAaN (ORCPT ); Thu, 28 Feb 2019 19:30:13 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Feb 2019 16:30:11 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,425,1544515200"; d="scan'208";a="148235200" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga004.fm.intel.com with ESMTP; 28 Feb 2019 16:30:10 -0800 Date: Thu, 28 Feb 2019 17:30:26 -0700 From: Keith Busch To: Austin.Bolen@dell.com Cc: hch@infradead.org, Alex_Gagniuc@Dellteam.com, torvalds@linux-foundation.org, keith.busch@intel.com, sagi@grimberg.me, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, axboe@fb.com, mr.nuke.me@gmail.com, hch@lst.de, jonathan.derrick@intel.com Subject: Re: [PATCH] nvme-pci: Prevent mmio reads if pci channel offline Message-ID: <20190301003026.GA22712@localhost.localdomain> References: <20190225155501.GI10237@localhost.localdomain> <940d608e1a044a54abcb9d65923951f3@ausx13mps317.AMER.DELL.COM> <443262761d0e41fbb46a46dab28759c2@AUSX13MPC131.AMER.DELL.COM> <20190228141655.GA18319@infradead.org> <883e2fad8f6e4791bfee2ec08992da39@AUSX13MPC131.AMER.DELL.COM> <20190228232020.GB22003@localhost.localdomain> <680f55f95e7547bdaffddce49772a5b7@AUSX13MPC131.AMER.DELL.COM> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <680f55f95e7547bdaffddce49772a5b7@AUSX13MPC131.AMER.DELL.COM> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 28, 2019 at 11:43:46PM +0000, Austin.Bolen@dell.com wrote: > On 2/28/2019 5:20 PM, Keith Busch wrote: > > SBR and Link Disable are done from the down stream port, though, so the > > host can still communicate with the function that took the link down. > > That's entirely different than taking the link down from the end device, > > so I'm not sure how NVMe can fix that. > > > > Agreed it is different. Here is one way they could have solved it: host > writes magic value to NSSRC but device latches this instead of > resetting. Then require host to do SBR. When device sees SBR with > magic value in NSSRC it does an NSSR. For single port drives, yes, but that wouldn't work so well for multi-port devices connected to different busses, maybe even across multiple hosts. The equivalent of an FLR across all ports should have been sufficient, IMO.