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=-5.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=no 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 5E2E0C4338F for ; Mon, 23 Aug 2021 14:06:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A3FA61206 for ; Mon, 23 Aug 2021 14:06:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229627AbhHWOGt (ORCPT ); Mon, 23 Aug 2021 10:06:49 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:54418 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229518AbhHWOGs (ORCPT ); Mon, 23 Aug 2021 10:06:48 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 17NE2ubY109623; Mon, 23 Aug 2021 10:05:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : in-reply-to : references : mime-version : content-type : content-transfer-encoding; s=pp1; bh=bOin9H3/j8g9XbLCcxMtctZkDI1hAxdofJouD39ZKKs=; b=Uj3MpLREZFTwpPG7riHPRe9kkdBOnR/AzPJTZR846c00HxqOOlyaDbEONKv0YrsHy4x9 B6BzEw/hdskdSJQ46JAaTcE0h65qT0jbEikRsWbDc9fIgTGbwEJuqr6QH8wY+/22qRiw IGKaXjYYMRukF0azjsr/DUsYlBHHyB/NuZldV31nLho7JpwH/IZtKTOL4meLf/L4mGAI zFxqwo5dCrcLkG/Zio50CzOXrtP7DWCwEEuyG/euSK6tfbowBnFEV6IaMnnY0kyo01XQ WNBYRPMH0W+6lZrc0e5+H8G3fR9TVvlPyJC/HaWhiHFJLSKALu/9ZJ+dgKE2lAUMUUlf bg== Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 3amamgw2fw-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Aug 2021 10:05:55 -0400 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 17NE3eWQ012401; Mon, 23 Aug 2021 14:05:52 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma03ams.nl.ibm.com with ESMTP id 3ajs48bcvh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Aug 2021 14:05:52 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 17NE5nQo23855460 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 23 Aug 2021 14:05:49 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5975F4C044; Mon, 23 Aug 2021 14:05:49 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D36274C046; Mon, 23 Aug 2021 14:05:48 +0000 (GMT) Received: from thinkpad (unknown [9.171.9.196]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 23 Aug 2021 14:05:48 +0000 (GMT) Date: Mon, 23 Aug 2021 16:05:46 +0200 From: Gerald Schaefer To: Christoph Hellwig Cc: Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Dan Williams , nvdimm@lists.linux.dev, linux-s390@vger.kernel.org Subject: Re: can we finally kill off CONFIG_FS_DAX_LIMITED Message-ID: <20210823160546.0bf243bf@thinkpad> In-Reply-To: <20210820054340.GA28560@lst.de> References: <20210820054340.GA28560@lst.de> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 1A_TPo4dkfWUK9cCFGq2PmlskZkAXvhC X-Proofpoint-GUID: 1A_TPo4dkfWUK9cCFGq2PmlskZkAXvhC X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-23_03:2021-08-23,2021-08-23 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 adultscore=0 malwarescore=0 mlxscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 mlxlogscore=779 priorityscore=1501 spamscore=0 suspectscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108230098 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Fri, 20 Aug 2021 07:43:40 +0200 Christoph Hellwig wrote: > Hi all, > > looking at the recent ZONE_DEVICE related changes we still have a > horrible maze of different code paths. I already suggested to > depend on ARCH_HAS_PTE_SPECIAL for ZONE_DEVICE there, which all modern > architectures have anyway. But the other odd special case is > CONFIG_FS_DAX_LIMITED which is just used for the xpram driver. Does > this driver still see use? If so can we make it behave like the > other DAX drivers and require a pgmap? I think the biggest missing > part would be to implement ARCH_HAS_PTE_DEVMAP for s390. Puh, yes, that seems to be needed in order to enable ZONE_DEVICE, and then we could use devm_memremap_pages(), at least that was my plan some time ago. However, either the ARCH_HAS_PTE_DEVMAP dependency is new, or I overlooked it before, but we do not have any free bits in the pte left, so this is not going to work. Would it strictly be necessary to implement ZONE_DEVICE, or would it be enough if we would use e.g. add_memory() instead of just adding the DCSS memory directly to the kernel mapping via vmem_add_mapping()? That way we might at least get the struct pages, but somehow it doesn't feel completely right.