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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BAF72C433F5 for ; Fri, 6 May 2022 11:06:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1389792AbiEFLKP (ORCPT ); Fri, 6 May 2022 07:10:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42742 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233719AbiEFLKO (ORCPT ); Fri, 6 May 2022 07:10:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6274051E57; Fri, 6 May 2022 04:06:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EF96161DEC; Fri, 6 May 2022 11:06:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2AA7FC385AA; Fri, 6 May 2022 11:06:26 +0000 (UTC) Date: Fri, 6 May 2022 12:06:22 +0100 From: Catalin Marinas To: "Leizhen (ThunderTown)" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org, Dave Young , Baoquan He , Vivek Goyal , Eric Biederman , kexec@lists.infradead.org, Will Deacon , linux-arm-kernel@lists.infradead.org, Rob Herring , Frank Rowand , devicetree@vger.kernel.org, Jonathan Corbet , linux-doc@vger.kernel.org, Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , Dave Kleikamp Subject: Re: [PATCH v23 3/6] arm64: kdump: Reimplement crashkernel=X Message-ID: References: <20220505091845.167-1-thunder.leizhen@huawei.com> <20220505091845.167-4-thunder.leizhen@huawei.com> <189f24a8-9e9b-b3e9-7ac5-935433ea575b@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <189f24a8-9e9b-b3e9-7ac5-935433ea575b@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, May 06, 2022 at 11:22:51AM +0800, Leizhen (ThunderTown) wrote: > On 2022/5/6 1:01, Catalin Marinas wrote: > > On Thu, May 05, 2022 at 05:18:42PM +0800, Zhen Lei wrote: > >> From: Chen Zhou > >> > >> There are following issues in arm64 kdump: > >> 1. We use crashkernel=X to reserve crashkernel in DMA zone, which > >> will fail when there is not enough low memory. > >> 2. If reserving crashkernel above DMA zone, in this case, crash dump > >> kernel will fail to boot because there is no low memory available > >> for allocation. > >> > >> To solve these issues, introduce crashkernel=X,[high,low]. > >> The "crashkernel=X,high" is used to select a region above DMA zone, and > >> the "crashkernel=Y,low" is used to allocate specified size low memory. > > > > Thanks for posting the simplified version, though the discussion with > > Baoquan is still ongoing. AFAICT there is no fallback if crashkernel= > > fails. The advantage with this series is cleaner code, we set the limits > > during parsing and don't have to adjust them if some of the first > > allocation failed. > > Yes, I'm currently implementing it in the simplest version, providing only > the most basic functions. Because the conclusions of this part of the discussion > are clear. I think I can send the fallback, default low size, and mapping optimization > patches separately after this basic version is merged. These three functions can > be discussed separately. This works for me. If we decide to go for fallbacks, it can be done as a separate patch. > >> + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); > >> + if (ret || !crash_size) > >> + return; > >> + > >> + /* > >> + * crashkernel=Y,low can be specified or not, but invalid value > >> + * is not allowed. > >> + */ > >> + ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base); > >> + if (ret && (ret != -ENOENT)) > >> + return; > >> + > >> + crash_max = CRASH_ADDR_HIGH_MAX; > >> + } > >> > >> crash_size = PAGE_ALIGN(crash_size); > >> > >> @@ -118,8 +159,7 @@ static void __init reserve_crashkernel(void) > >> if (crash_base) > >> crash_max = crash_base + crash_size; > >> > >> - /* Current arm64 boot protocol requires 2MB alignment */ > >> - crash_base = memblock_phys_alloc_range(crash_size, SZ_2M, > >> + crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, > >> crash_base, crash_max); > >> if (!crash_base) { > >> pr_warn("cannot allocate crashkernel (size:0x%llx)\n", > > > > I personally like this but let's see how the other thread goes. I guess > > Me too. This fallback complicates code logic more than just a little. > I'm not sure why someone would rather add fallback than change the bootup > options to crashkernel=X,[high|low]. Perhaps fallback to high/low is a better > compatible and extended mode when crashkernel=X fails to reserve memory. And > the code logic will be much clearer. > > //parse crashkernel=X //To simplify the discussion, Ignore [@offset] > crash_base = memblock_phys_alloc_range() > if (!crash_base || /* crashkernel=X is not specified */) { > //parse crashkernel=X,[high,low] > //reserve high/low memory > } > > So that, the following three modes are supported: > 1) crashkernel=X[@offset] > 2) crashkernel=X,high crashkernel=X,low > 3) crashkernel=X[@offset] crashkernel=X,high [crashkernel=Y,low] The whole interface isn't great but if we add fall-back options, I'd rather stick close to what x86 does. IOW, if crashkernel=X is provided, ignore explicit high/low (so 3 does not exist). (if I had added it from the beginning, I'd have removed 'high' completely and allow crashkernel=X to fall-back to 'high' with an optional explicit 'low' or 'dma' if the default is not sufficient; but I think there's too much bikeshedding already) > > if we want a fallback, it would come just before the check the above: > > > > if (!crash_base && crash_max != CRASH_ADDR_HIGH_MAX) { > > /* attempt high allocation with default low */ > > if (!crash_low_size) > > crash_low_size = some default; > > crash_max = CRASH_ADDR_LOW_MAX; > > crash_max = CRASH_ADDR_HIGH_MAX; We should fallback to high memory now. Yes, that's the idea. Anyway, please post the current series with the minor updates I mentioned and we can add a fallback patch (or two) on top. Thanks. -- Catalin