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=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 63518C433E0 for ; Mon, 25 May 2020 12:01:28 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 312292071A for ; Mon, 25 May 2020 12:01:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 312292071A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 7AB6512227BEC; Mon, 25 May 2020 04:57:30 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=vaibhav@linux.ibm.com; receiver= Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 2092612227BEA for ; Mon, 25 May 2020 04:57:27 -0700 (PDT) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 04PBVAUQ035241; Mon, 25 May 2020 08:00:50 -0400 Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 316weudjhj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 25 May 2020 08:00:50 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 04PBvJuB031814; Mon, 25 May 2020 12:00:48 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma04ams.nl.ibm.com with ESMTP id 316uf8v17p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 25 May 2020 12:00:48 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 04PC0kQq60424296 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 25 May 2020 12:00:46 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5F2834C050; Mon, 25 May 2020 12:00:46 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 163AE4C046; Mon, 25 May 2020 12:00:43 +0000 (GMT) Received: from vajain21-in-ibm-com (unknown [9.102.3.198]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 25 May 2020 12:00:42 +0000 (GMT) Received: by vajain21-in-ibm-com (sSMTP sendmail emulation); Mon, 25 May 2020 17:30:42 +0530 From: Vaibhav Jain To: Michael Ellerman , Ira Weiny Subject: Re: [RESEND PATCH v7 4/5] ndctl/papr_scm, uapi: Add support for PAPR nvdimm specific methods In-Reply-To: <87ftbswhb6.fsf@linux.ibm.com> References: <20200519190058.257981-1-vaibhav@linux.ibm.com> <20200519190058.257981-5-vaibhav@linux.ibm.com> <20200520153209.GC3660833@iweiny-DESK2.sc.intel.com> <87367t941j.fsf@mpe.ellerman.id.au> <87ftbswhb6.fsf@linux.ibm.com> Date: Mon, 25 May 2020 17:30:42 +0530 Message-ID: <87a71ww7f9.fsf@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-25_05:2020-05-25,2020-05-25 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 bulkscore=0 mlxscore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 adultscore=0 mlxlogscore=999 priorityscore=1501 clxscore=1015 suspectscore=0 cotscore=-2147483648 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005250087 Message-ID-Hash: ESAPQZH5DHAUHHWWY55XGW4FX2JXY53S X-Message-ID-Hash: ESAPQZH5DHAUHHWWY55XGW4FX2JXY53S X-MailFrom: vaibhav@linux.ibm.com X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: "Aneesh Kumar K . V" , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Steven Rostedt , linux-nvdimm@lists.01.org X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Ira, Mpe and Aneesh, Vaibhav Jain writes: > Michael Ellerman writes: > >> Ira Weiny writes: >>> On Wed, May 20, 2020 at 12:30:57AM +0530, Vaibhav Jain wrote: >>>> Introduce support for Papr nvDimm Specific Methods (PDSM) in papr_scm >>>> modules and add the command family to the white list of NVDIMM command >>>> sets. Also advertise support for ND_CMD_CALL for the dimm >>>> command mask and implement necessary scaffolding in the module to >>>> handle ND_CMD_CALL ioctl and PDSM requests that we receive. >> ... >>>> + * >>>> + * Payload Version: >>>> + * >>>> + * A 'payload_version' field is present in PDSM header that indicates a specific >>>> + * version of the structure present in PDSM Payload for a given PDSM command. >>>> + * This provides backward compatibility in case the PDSM Payload structure >>>> + * evolves and different structures are supported by 'papr_scm' and 'libndctl'. >>>> + * >>>> + * When sending a PDSM Payload to 'papr_scm', 'libndctl' should send the version >>>> + * of the payload struct it supports via 'payload_version' field. The 'papr_scm' >>>> + * module when servicing the PDSM envelope checks the 'payload_version' and then >>>> + * uses 'payload struct version' == MIN('payload_version field', >>>> + * 'max payload-struct-version supported by papr_scm') to service the PDSM. >>>> + * After servicing the PDSM, 'papr_scm' put the negotiated version of payload >>>> + * struct in returned 'payload_version' field. >>> >>> FWIW many people believe using a size rather than version is more sustainable. >>> It is expected that new payload structures are larger (more features) than the >>> previous payload structure. >>> >>> I can't find references at the moment through. >> >> I think clone_args is a good modern example: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/sched.h#n88 >> >> cheers > > Thank Ira and Mpe for pointing this out. I looked into how clone3 sycall > handles clone_args and few differences came out: > > * Unlike clone_args that are always transferred in one direction from > user-space to kernel, payload contents of pdsms are transferred in both > directions. Having a single version number makes it easier for > user-space and kernel to determine what data will be exchanged. > > * For PDSMs, the version number is negotiated between libndctl and > kernel. For example in case kernel only supports an older version of > a structure, its free to send a lower version number back to > libndctl. Such negotiations doesnt happen with clone3 syscall. If you are ok with the explaination above please let me know. I will quickly spin off a v8 addressing your review comments. Thanks, -- Cheers ~ Vaibhav _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org