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 84DE5C4338F for ; Mon, 23 Aug 2021 19:47:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61789613A6 for ; Mon, 23 Aug 2021 19:47:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230187AbhHWTsF (ORCPT ); Mon, 23 Aug 2021 15:48:05 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:9790 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229558AbhHWTsF (ORCPT ); Mon, 23 Aug 2021 15:48:05 -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 17NJWsdK179055; Mon, 23 Aug 2021 15:47:16 -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=PJxEuxRmEIHlb0OAOevNy3NFmY3DbCPNlzGEHrbXp00=; b=XwxKGdZ79GK09DXzh1sxkLlUIjH/VpGHs1jTA2+uGIQQcNIUBkFOGoEe96EjfWfkGd6R G7M9mBfp3jgf9G4GC9E7TfDF4soGFzFYJsL4lFd2Txm3tyt9hAAlppEwPChJv3TxPkCT J+M0PZ2I0eoMSc+qb7YPIziFPKbH9Yn8U4tkfe39uxZos6FVhuJcreVN65Z3YCsTApx6 4Zv56EdVvFhWKejZbyOcRiTysGol8biDkhEk6jS93tditoXli+U/dlmwyU8vTGLXbUak C5d8tnILW8PDvjjqerwxGU35vVjHHqdCyvb7t8WWsKS+nEVaf+1h1vjmYiosgk4jzRhB OA== Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com [159.122.73.71]) by mx0a-001b2d01.pphosted.com with ESMTP id 3amhemh1vs-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Aug 2021 15:47:16 -0400 Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1]) by ppma02fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 17NJgPrV030829; Mon, 23 Aug 2021 19:47:14 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma02fra.de.ibm.com with ESMTP id 3ajs48b95n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Aug 2021 19:47:14 +0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 17NJlARH53018902 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 23 Aug 2021 19:47:10 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 816DCAE056; Mon, 23 Aug 2021 19:47:10 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 11114AE051; Mon, 23 Aug 2021 19:47:10 +0000 (GMT) Received: from thinkpad (unknown [9.171.9.196]) by d06av26.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 23 Aug 2021 19:47:09 +0000 (GMT) Date: Mon, 23 Aug 2021 21:47:08 +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: <20210823214708.77979b3f@thinkpad> In-Reply-To: <20210823160546.0bf243bf@thinkpad> References: <20210820054340.GA28560@lst.de> <20210823160546.0bf243bf@thinkpad> 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-GUID: gxt_o5tcJYTtr5UwTuOdZVZ3Rjui3-TT X-Proofpoint-ORIG-GUID: gxt_o5tcJYTtr5UwTuOdZVZ3Rjui3-TT X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-23_04:2021-08-23,2021-08-23 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxlogscore=801 adultscore=0 impostorscore=0 phishscore=0 mlxscore=0 bulkscore=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108230133 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Mon, 23 Aug 2021 16:05:46 +0200 Gerald Schaefer wrote: > 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 Oh, we do have PTE_SPECIAL, actually that took away the last free bit in the pte. So, if there is a chance that ZONE_DEVICE would depend on PTE_SPECIAL instead of PTE_DEVMAP, we might be back in the game and get rid of that CONFIG_FS_DAX_LIMITED. Or did you rather mean depend on ARCH_HAS_PTE_SPECIAL on top of ARCH_HAS_PTE_DEVMAP? > > 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.