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Fri, 17 Nov 2023 13:56:53 GMT Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2C47E2004B; Fri, 17 Nov 2023 13:56:53 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4222220040; Fri, 17 Nov 2023 13:56:52 +0000 (GMT) Received: from li-2b55cdcc-350b-11b2-a85c-a78bff51fc11.ibm.com (unknown [9.171.27.169]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 17 Nov 2023 13:56:52 +0000 (GMT) Date: Fri, 17 Nov 2023 14:56:50 +0100 From: Sumanth Korikkar To: David Hildenbrand Cc: linux-mm , Andrew Morton , Oscar Salvador , Michal Hocko , "Aneesh Kumar K.V" , Anshuman Khandual , Gerald Schaefer , Alexander Gordeev , Heiko Carstens , Vasily Gorbik , linux-s390 , LKML Subject: Re: [PATCH 0/8] implement "memmap on memory" feature on s390 Message-ID: References: <20231114180238.1522782-1-sumanthk@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 1GifuvWjsj_2j5Z19rWdfUA7kA8hPsNg X-Proofpoint-ORIG-GUID: AypSkno244K_SEEdsFNfx71CpUm8yrQU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-17_12,2023-11-17_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=12 suspectscore=0 bulkscore=0 clxscore=1015 phishscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 mlxscore=12 mlxlogscore=87 malwarescore=0 impostorscore=0 spamscore=12 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311170103 X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8CE62120025 X-Stat-Signature: 6rmac4iqgbyxcboxf5b1p7d7hhhnkgd1 X-HE-Tag: 1700229422-648050 X-HE-Meta: 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 QUf4X5ay e6r9jBPjGIZYduLSKBxOPKpn94U2kvC17V5dE/coOcXHFsg2rGPdpbikMnPjWP48ezg/p550bl7iozSnRFps8fZmp35xXYdJyoo0n0dXyAerQQbJ7imzrN9Mb5Ox1TaBB9ClebSfoIKQy80c= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Nov 17, 2023 at 12:08:31AM +0100, David Hildenbrand wrote: > On 14.11.23 19:02, Sumanth Korikkar wrote: > > Hi All, > > > > The patch series implements "memmap on memory" feature on s390 and > > provides the necessary fixes for it. > > Thinking about this, one thing that makes s390x different from all the other > architectures in this series is the altmap handling. > > I'm curious, why is that even required? > > A memmep that is not marked as online in the section should not be touched > by anybody (except memory onlining code :) ). And if we do, it's usually a > BUG because that memmap might contain garbage/be poisoned or completely > stale, so we might want to track that down and fix it in any case. > > So what speaks against just leaving add_memory() populate the memmap from > the altmap? Then, also the page tables for the memmap are already in place > when onlining memory. > we do have page_init_poison() in sparse_add_section() which should be handled later then. not in add_pages() > > Then, adding two new notifier calls on start of memory_block_online() called > something like MEM_PREPARE_ONLINE and end the end of memory_block_offline() > called something like MEM_FINISH_OFFLINE is still suboptimal, but that's > where standby memory could be activated/deactivated, without messing with > the altmap. > > That way, the only s390x specific thing is that the memmap that should not > be touched by anybody is actually inaccessible, and you'd > activate/deactivate simply from the new notifier calls just the way we used > to do. ok. Thanks