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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 847C0C04A95 for ; Tue, 25 Oct 2022 10:32:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 13E298E0002; Tue, 25 Oct 2022 06:32:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0EDE98E0001; Tue, 25 Oct 2022 06:32:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F1EC18E0002; Tue, 25 Oct 2022 06:32:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id DEF4A8E0001 for ; Tue, 25 Oct 2022 06:32:01 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id A4809160D39 for ; Tue, 25 Oct 2022 10:32:01 +0000 (UTC) X-FDA: 80059106442.20.E590D1C Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by imf05.hostedemail.com (Postfix) with ESMTP id C3675100019 for ; Tue, 25 Oct 2022 10:32:00 +0000 (UTC) Received: from zn.tnic (p200300ea9733e753329c23fffea6a903.dip0.t-ipconnect.de [IPv6:2003:ea:9733:e753:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 594351EC04CB; Tue, 25 Oct 2022 12:31:59 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1666693919; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=ai++jgLmenhahiBLse1vLJYEB/bd3+G6lQ4acR+CSyY=; b=P0z3I0xwj2YyygD/nk8kPmHQz8xOPhwrirQ4FKwWdW+LYy3NzSZiRAcnVsDad4/4TyA+Id C+dIkSRTyCBWdW6AUgSdcRLJzREMPfzuSdYMC78Rx5/r6BqAXRtj4u1KDAn+pdlC6xIfU4 MRXEub1PBMS0Jdrf8LEWllVjz5u5FYg= Date: Tue, 25 Oct 2022 12:31:59 +0200 From: Borislav Petkov To: Baoquan He Cc: Eric DeVolder , Oscar Salvador , Andrew Morton , david@redhat.com, linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, sourabhjain@linux.ibm.com, linux-mm@kvack.org Subject: Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support Message-ID: References: <53aed03e-2eed-09b1-9532-fe4e497ea47d@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666693921; a=rsa-sha256; cv=none; b=gASQJMKZDJWxqdUzSU7jgzZi80Il9Go6t+okf9PzvY95+jMJJ/xHvM6GSeGFEABAQG2za4 7mE1L/yAYzU8zJgWsmUf+oJIyLFAPMEk0fxKqJp9xhJIeqYJYB3/Z5MCwvuAbr2XEX4pdE qdhmUuupOXg1/RIrMi8FlitV9IllJUI= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=alien8.de header.s=dkim header.b=P0z3I0xw; dmarc=pass (policy=none) header.from=alien8.de; spf=pass (imf05.hostedemail.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) smtp.mailfrom=bp@alien8.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666693921; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ai++jgLmenhahiBLse1vLJYEB/bd3+G6lQ4acR+CSyY=; b=PbP2gBwfTfiftvuMALt7fZ+WhZJ8sqzNEE3VnBGduPMoaP18l9R1N6dxBvFhBEVUZxhsE8 OF/KRsjM1cm99mNIAgSIyeXHIJ33YxG0Ucvdw95xHKp6cLrZnRTC5jfldsU055+WaO6HSX 6GC+cpGpJ86Omhp5yA5TTqmbwR8fR9Q= X-Rspamd-Queue-Id: C3675100019 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=alien8.de header.s=dkim header.b=P0z3I0xw; dmarc=pass (policy=none) header.from=alien8.de; spf=pass (imf05.hostedemail.com: domain of bp@alien8.de designates 5.9.137.197 as permitted sender) smtp.mailfrom=bp@alien8.de X-Rspamd-Server: rspam12 X-Rspam-User: X-Stat-Signature: fsgjhajdzzbhctqch158s8dpiotm34hm X-HE-Tag: 1666693920-985302 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: On Thu, Oct 13, 2022 at 10:57:28AM +0800, Baoquan He wrote: > The concern to range number mainly is on Virt guest systems. And why would virt emulate 1K hotpluggable DIMM slots and not emulate a real machine? > On baremetal system, basically only very high end server support > memory hotplug. I ever visited customer's lab and saw one server, > it owns 8 slots, on each slot a box containing about 20 cpus and 2T > memory at most can be plugged in at one time. So people won't make too > many slots for hotplugging since it's too expensive. There you have it - the persuading argument. > I checked user space kexec code, the maximum memory range number is > honored to x86_64 because of a HPE SGI system. After that, nobody > complains about it. Please see below user space kexec-tools commit in > https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git > > The memory ranges may be not all made by different DIMM slots, could be > firmware reservatoin, e.g efi/BIOS diggged out physical memory, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ I don't know what that means. If it is firmware crap, you want to exclude that from kdump anyway. > Now CONFIG_NR_CPUS has the maximum number as 8192. And user space > kexec-tools has maximum memory range number as 2048. We can take > the current 8192 + 2048 = 10K as default value conservatively. Or > take 8192 + 2048 * 2 = 12K which has two times of maximum memory range > bumber in kexec-tools. What do you think? I still think that we should stick to reality and support what is possible not what is potentially and theoretically there. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette