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 B0FE8C52D70 for ; Tue, 6 Aug 2024 20:45:49 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=RtaC8Q2Wyc0vqC7sNaQA1Oq2D3bAl2UMSDBnZibVVBk=; b=zKhD1SWAFJzUDcE6WUGzviTn/Q Oq6yM0TFIS43gxCeY08yOQyGOSofuicaNt6SffuT4hxMiWm5ZPQvB6dXk4r0VpmBNCM0ZmVs0zrT6 uuNoqt7aKlI6R2gt0phbKXbORxaUZW9VanTeV4APAfI5r98s9AMGPr3PWJzS9R/yS4rrdwkcvt1w/ +73PEFcg9l1HpknMWAFZzwEWdEqIR0Gex0L624HzVMpKisvfqpHVZflhWhotLlgYPRfS8iutYPc02 skCjGGBh0skl0jjmGQz0znfpAjbHx4WMYOVEfDbmzyvF8UgTm48rkIXSyrYGn2SKd3M28wRV70Y/o +BMhAkRA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbR3q-00000002rW3-3GFL; Tue, 06 Aug 2024 20:45:38 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbPxP-00000002iI7-2YQD; Tue, 06 Aug 2024 19:34:55 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=RtaC8Q2Wyc0vqC7sNaQA1Oq2D3bAl2UMSDBnZibVVBk=; b=mLRYQCRUp8BLGuw9BvmAPhQ1xf KPAJx5BzHTvcozJSepwASLNw3vxIUpyVEbRBcB8wPNgYKxYCpdZKC28aU6/rezN9iRsECB7Hsj/On WSYRKAO0NiycuwqmZKf3d1s/VOxXq4PlF8ayo4Krk85kJhvMeTaUWO+6GHcnniQcDzyh9UzzXzqgR P4h2vFzQ1pS+S8ZosAdbHvKusFhjKDWArc3TvBEx/CEdRZZF7gAdslWvyr3fwGXPv5Fi0q9ZLSS9v Zyao3qvKSL2ykYUsfxeLkYLw8JHqxphX+oeU+oM2ZP7vmsvf+L5EGFmxOZvRRY2rOtY66WaBWWNiN ReJxLd7Q==; Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by desiato.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbPxM-00000006W5T-0CDD; Tue, 06 Aug 2024 19:34:54 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 87A0160FB5; Tue, 6 Aug 2024 19:34:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98C42C32786; Tue, 6 Aug 2024 19:34:44 +0000 (UTC) Date: Tue, 6 Aug 2024 20:34:42 +0100 From: Catalin Marinas To: Baoquan He Cc: Jinjie Ruan , vgoyal@redhat.com, dyoung@redhat.com, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, chenjiahao16@huawei.com, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Will Deacon Subject: Re: [PATCH -next] crash: Fix riscv64 crash memory reserve dead loop Message-ID: References: <20240802090105.3871929-1-ruanjinjie@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240806_203452_559880_6D7CCB00 X-CRM114-Status: GOOD ( 27.43 ) 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 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. Thanks. -- Catalin