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 2DF6EEB64DC for ; Fri, 21 Jul 2023 10:36:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 810FD2801B0; Fri, 21 Jul 2023 06:36:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 79A362801A0; Fri, 21 Jul 2023 06:36:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 63AE32801B0; Fri, 21 Jul 2023 06:36:38 -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 4FE682801A0 for ; Fri, 21 Jul 2023 06:36:38 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 25AD51A0224 for ; Fri, 21 Jul 2023 10:36:38 +0000 (UTC) X-FDA: 81035265276.22.341669C Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf04.hostedemail.com (Postfix) with ESMTP id 6A9304000D for ; Fri, 21 Jul 2023 10:36:36 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="L/UWsDU4"; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of will@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=will@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689935796; 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=rYOneG0LaPMmvmGwT886AllQGDt87fxEuEIxqQeeL/U=; b=KR+u9eRfSV4RfagnrIsj8hr9ax44Nj+GNLO3v5dg7gXo8z1DDTWTQ1pg9k1VTmW0zTFpS4 ve+sg5mUsSRmUVujK6qsC38ef2ib5Ew9GJEDU+aFjgnKR4tF6C/d6DOpPvNWXiSkKS6Spc AZc+Yrmj8geZ0WotOXVlllsLb492UtA= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="L/UWsDU4"; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf04.hostedemail.com: domain of will@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=will@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689935796; a=rsa-sha256; cv=none; b=BDSfehOxq2DgYWslw9z3gG69Ylq2qgczSo08twjnUYdCNtpEDiWb3o+8xv37/HwQvYFSYR sOvISkraRP0L8L1ctDAE8Gq177GgcqZhkYqLGOnpDxy4Phx4RuI1bElnBI1kNPyO0PffeF +6vYi8OzFrgJnk33eghSeVudh/kxhYA= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4186E61059; Fri, 21 Jul 2023 10:36:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA1F3C433C7; Fri, 21 Jul 2023 10:36:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689935794; bh=d3RDQYHBiofoLtTOsVGd0+hDYbPOksiQmmPkI1vmf0M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=L/UWsDU4VYCbs4LhUhJWB2TbtnSnTADPvw3/xdSxrWWYc5Ut5Kz0JBEQi501rF5rn Y5azfgrgwsSWJUNSm/tGZLMZBeeqhNYVZKOkaKBSv9GTlgyrWB24l//X2DK7XaEhCg udrRlLvqWmAG9oBEYFTQwpztGAbWcUkcpX3Jsxd5ta/lmAlDSS3worDmILpldn3Xko zsWZ2TzZYs1AGUQk74sSHZwVE6SZAkO5pAMlnoaumMDvefFn3MYhyE2KJxG2SzVOdA L0dKvaEZgcFneP70XGrWfgG0RXib7YeLcsBYKbTh+GmBEGXgAmvAYWFbzqDfp0u5tW S3PkKsigEKd+Q== Date: Fri, 21 Jul 2023 11:36:29 +0100 From: Will Deacon To: Wupeng Ma Cc: catalin.marinas@arm.com, akpm@linux-foundation.org, sudaraja@codeaurora.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com, linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, anshuman.khandual@arm.com Subject: Re: [RFC PATCH] arm64: mm: Fix kernel page tables incorrectly deleted during memory removal Message-ID: <20230721103628.GA12601@willie-the-truck> References: <20230717115150.1806954-1-mawupeng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230717115150.1806954-1-mawupeng1@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6A9304000D X-Stat-Signature: ad33b1ti8n3kep3xmgkagpry6uiqnikk X-HE-Tag: 1689935796-803470 X-HE-Meta: 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 9ogig6ms NA2R0dviubRk6JXqPNpIB/ewZySBIzyJXYI6yKKeMxFT+Eai7KNyIt3G9qxxd1NO1/DRc4AWLq6D7Q0RcW6EvQRlHKy3Vi78mnVuLpvUjSa0Gd92bCtBgovMLNY17XmgSRtwHTip1xRz4zIemO0d9IT1I1rT3a8F3uo8Pxl/2L1z0JHR8aw1KUUMw51WsdhHmeCC+h/okGw0MQmFozVmJP3qHkP5c6jt+M6lMjziBnIaL6uX528e8lTzFkUJFN4eicrmDcSz3UFz5qi6iL6Ke6udQBhxOn6PBY4MBbbWFOBWVikQyN2YAKyHtEg== 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 Mon, Jul 17, 2023 at 07:51:50PM +0800, Wupeng Ma wrote: > From: Ma Wupeng > > During our test, we found that kernel page table may be unexpectedly > cleared with rodata off. The root cause is that the kernel page is > initialized with pud size(1G block mapping) while offline is memory > block size(MIN_MEMORY_BLOCK_SIZE 128M), eg, if 2G memory is hot-added, > when offline a memory block, the call trace is shown below, > > offline_and_remove_memory > try_remove_memory > arch_remove_memory > __remove_pgd_mapping > unmap_hotplug_range > unmap_hotplug_p4d_range > unmap_hotplug_pud_range > if (pud_sect(pud)) > pud_clear(pudp); Sorry, but I'm struggling to understand the problem here. If we're adding and removing a 2G memory region, why _wouldn't_ we want to use large 1GiB mappings? Or are you saying that only a subset of the memory is removed, but we then accidentally unmap the whole thing? > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 95d360805f8a..44c724ce4f70 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -44,6 +44,7 @@ > #define NO_BLOCK_MAPPINGS BIT(0) > #define NO_CONT_MAPPINGS BIT(1) > #define NO_EXEC_MAPPINGS BIT(2) /* assumes FEAT_HPDS is not used */ > +#define NO_PUD_MAPPINGS BIT(3) > > int idmap_t0sz __ro_after_init; > > @@ -344,7 +345,7 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end, > */ > if (pud_sect_supported() && > ((addr | next | phys) & ~PUD_MASK) == 0 && > - (flags & NO_BLOCK_MAPPINGS) == 0) { > + (flags & (NO_BLOCK_MAPPINGS | NO_PUD_MAPPINGS)) == 0) { > pud_set_huge(pudp, phys, prot); > > /* > @@ -1305,7 +1306,7 @@ struct range arch_get_mappable_range(void) > int arch_add_memory(int nid, u64 start, u64 size, > struct mhp_params *params) > { > - int ret, flags = NO_EXEC_MAPPINGS; > + int ret, flags = NO_EXEC_MAPPINGS | NO_PUD_MAPPINGS; I think we should allow large mappings here and instead prevent partial removal of the block, if that's what is causing the issue. Will