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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BAE57C52D73 for ; Thu, 8 Aug 2024 07:57:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:CC:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mRKkUcOR/nTSmrxy4zUGUMVZV5rWxQdf0VKY/u9GMyE=; b=sXkTGcZXwewG0xCq/bRBddi9zl AapYHLH7ybwWXaL9leARxSI8Q9He+Q+Nq7mp37XylUdAPdhBHv1Yf5l45D3NUHQClPQ9RBhjbl+pQ kZEVktILubvTotg/W1g9rBDmS1psiJQKNNKqQLAqDGsgVNXSHiOypADuo6AyaXtpW7AGrTeDAKNWQ DsObDnW1niRZQhdnTjxW5iN5MX8AB3ZEIh1Y7feDOyyADpwk5Zb8U1dEZ4pf92sIDpcWMHP0d+aHP GCpuzeH+jS3EP8qfHvythoHc3/tkykdECwpEz8MsJ40D4FHwmJeZ64e7Q64kFYV7NfAptQx5rJvPT 1IubVNrA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sby1M-00000007VBJ-2r8B; Thu, 08 Aug 2024 07:57:16 +0000 Received: from szxga02-in.huawei.com ([45.249.212.188]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sby0n-00000007V5D-3AWc; Thu, 08 Aug 2024 07:56:43 +0000 Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4WffV54tM4zpTDg; Thu, 8 Aug 2024 15:55:25 +0800 (CST) Received: from kwepemi100008.china.huawei.com (unknown [7.221.188.57]) by mail.maildlp.com (Postfix) with ESMTPS id 20577140604; Thu, 8 Aug 2024 15:56:37 +0800 (CST) Received: from [10.67.109.254] (10.67.109.254) by kwepemi100008.china.huawei.com (7.221.188.57) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 8 Aug 2024 15:56:36 +0800 Message-ID: Date: Thu, 8 Aug 2024 15:56:35 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH -next] crash: Fix riscv64 crash memory reserve dead loop Content-Language: en-US To: Catalin Marinas , Baoquan He CC: , , , , , , , , , , , Will Deacon References: <20240802090105.3871929-1-ruanjinjie@huawei.com> From: Jinjie Ruan In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.109.254] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemi100008.china.huawei.com (7.221.188.57) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240808_005642_144313_4AE8B7D9 X-CRM114-Status: GOOD ( 18.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2024/8/7 3:34, Catalin Marinas wrote: > On Tue, Aug 06, 2024 at 08:10:30PM +0100, Catalin Marinas wrote: >> On Fri, Aug 02, 2024 at 06:11:01PM +0800, Baoquan He wrote: >>> On 08/02/24 at 05:01pm, Jinjie Ruan wrote: >>>> On RISCV64 Qemu machine with 512MB memory, cmdline "crashkernel=500M,high" >>>> will cause system stall as below: >>>> >>>> Zone ranges: >>>> DMA32 [mem 0x0000000080000000-0x000000009fffffff] >>>> Normal empty >>>> Movable zone start for each node >>>> Early memory node ranges >>>> node 0: [mem 0x0000000080000000-0x000000008005ffff] >>>> node 0: [mem 0x0000000080060000-0x000000009fffffff] >>>> Initmem setup node 0 [mem 0x0000000080000000-0x000000009fffffff] >>>> (stall here) >>>> >>>> commit 5d99cadf1568 ("crash: fix x86_32 crash memory reserve dead loop >>>> bug") fix this on 32-bit architecture. However, the problem is not >>>> completely solved. If `CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX` on 64-bit >>>> architecture, for example, when system memory is equal to >>>> CRASH_ADDR_LOW_MAX on RISCV64, the following infinite loop will also occur: >>> >>> Interesting, I didn't expect risc-v defining them like these. >>> >>> #define CRASH_ADDR_LOW_MAX dma32_phys_limit >>> #define CRASH_ADDR_HIGH_MAX memblock_end_of_DRAM() >> >> arm64 defines the high limit as PHYS_MASK+1, it doesn't need to be >> dynamic and x86 does something similar (SZ_64T). Not sure why the >> generic code and riscv define it like this. >> >>>> -> reserve_crashkernel_generic() and high is true >>>> -> alloc at [CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX] fail >>>> -> alloc at [0, CRASH_ADDR_LOW_MAX] fail and repeatedly >>>> (because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX). >>>> >>>> Before refactor in commit 9c08a2a139fe ("x86: kdump: use generic interface >>>> to simplify crashkernel reservation code"), x86 do not try to reserve crash >>>> memory at low if it fails to alloc above high 4G. However before refator in >>>> commit fdc268232dbba ("arm64: kdump: use generic interface to simplify >>>> crashkernel reservation"), arm64 try to reserve crash memory at low if it >>>> fails above high 4G. For 64-bit systems, this attempt is less beneficial >>>> than the opposite, remove it to fix this bug and align with native x86 >>>> implementation. >>> >>> And I don't like the idea crashkernel=,high failure will fallback to >>> attempt in low area, so this looks good to me. >> >> Well, I kind of liked this behaviour. One can specify ,high as a >> preference rather than forcing a range. The arm64 land has different >> platforms with some constrained memory layouts. Such fallback works well >> as a default command line option shipped with distros without having to >> guess the SoC memory layout. > > I haven't tried but it's possible that this patch also breaks those > arm64 platforms with all RAM above 4GB when CRASH_ADDR_LOW_MAX is > memblock_end_of_DRAM(). Here all memory would be low and in the absence > of no fallback, it fails to allocate. > > So, my strong preference would be to re-instate the current behaviour > and work around the infinite loop in a different way. Hi, baoquan, What's your opinion? Only this patch should be re-instate or all the 3 dead loop fix patch? > > Thanks. >