From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g9t5009.houston.hpe.com (g9t5009.houston.hpe.com [15.241.48.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 7349121B02B8B for ; Thu, 29 Jun 2017 15:33:55 -0700 (PDT) Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges References: <149875877608.10031.17813337234536358002.stgit@dwillia2-desk3.amr.corp.intel.com> <149875884190.10031.6179599135820559644.stgit@dwillia2-desk3.amr.corp.intel.com> <595552F5.5040008@hpe.com> <59556E37.80808@hpe.com> From: Linda Knippers Message-ID: <595580A6.9000004@hpe.com> Date: Thu, 29 Jun 2017 18:35:18 -0400 MIME-Version: 1.0 In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Dan Williams Cc: Jan Kara , Matthew Wilcox , X86 ML , "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , Al Viro , linux-fsdevel , Christoph Hellwig List-ID: On 06/29/2017 06:28 PM, Dan Williams wrote: > On Thu, Jun 29, 2017 at 3:12 PM, Linda Knippers wrote: > [..] >>> The /dev/pmem >>> device name just tells you that your block device is hosted by a >>> driver that knows how to handle persistent memory constraints, but any >>> other details about the nature of the address range need to come from >>> other sources of information, and potentially information sources that >>> the kernel does not know about. >> >> >> I'm asking about the other source of information in this specific case >> where we're exposing pmem devices that will never ever be persistent. >> Before we add these devices, I think we should be able to tell the user >> how they can know the properties of the underlying device. > > The only way I can think to indicate this is with a platform + device > whitelist in a tool like ndctl. Where the tool says "yes, these > xyz-vendor DIMMs on this abc-vendor platform with this 123-version > BIOS" is a known good persistent configuration. Doesn't the kernel know that something will never ever be persistent because the NFIT type says NFIT_SPA_VDISK, NFIT_SPA_VCD, or NFIT_SPA_VOLATILE? That's the case I'm asking about here. In this patch, you're adding support for creating /dev/pmem devices for those address ranges. My question is how the admin/user knows that those devices will never ever be persistent. I don't think we need ndctl to know which vendors' hardware/firmware actually works as advertised. -- ljk _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751715AbdF2Wfc (ORCPT ); Thu, 29 Jun 2017 18:35:32 -0400 Received: from g2t1383g.austin.hpe.com ([15.233.16.89]:7421 "EHLO g2t1383g.austin.hpe.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751532AbdF2Wfa (ORCPT ); Thu, 29 Jun 2017 18:35:30 -0400 Authentication-Results: hpe.com; dkim=none (message not signed) header.d=none;hpe.com; dmarc=none action=none header.from=hpe.com; Subject: Re: [PATCH v4 12/16] libnvdimm, nfit: enable support for volatile ranges To: Dan Williams References: <149875877608.10031.17813337234536358002.stgit@dwillia2-desk3.amr.corp.intel.com> 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X-MS-Exchange-Transport-CrossTenantHeadersStamped: TU4PR84MB0079 X-OriginatorOrg: hpe.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/29/2017 06:28 PM, Dan Williams wrote: > On Thu, Jun 29, 2017 at 3:12 PM, Linda Knippers wrote: > [..] >>> The /dev/pmem >>> device name just tells you that your block device is hosted by a >>> driver that knows how to handle persistent memory constraints, but any >>> other details about the nature of the address range need to come from >>> other sources of information, and potentially information sources that >>> the kernel does not know about. >> >> >> I'm asking about the other source of information in this specific case >> where we're exposing pmem devices that will never ever be persistent. >> Before we add these devices, I think we should be able to tell the user >> how they can know the properties of the underlying device. > > The only way I can think to indicate this is with a platform + device > whitelist in a tool like ndctl. Where the tool says "yes, these > xyz-vendor DIMMs on this abc-vendor platform with this 123-version > BIOS" is a known good persistent configuration. Doesn't the kernel know that something will never ever be persistent because the NFIT type says NFIT_SPA_VDISK, NFIT_SPA_VCD, or NFIT_SPA_VOLATILE? That's the case I'm asking about here. In this patch, you're adding support for creating /dev/pmem devices for those address ranges. My question is how the admin/user knows that those devices will never ever be persistent. I don't think we need ndctl to know which vendors' hardware/firmware actually works as advertised. -- ljk