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 1F2F2C4332F for ; Fri, 6 May 2022 12:35:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347143AbiEFMjc (ORCPT ); Fri, 6 May 2022 08:39:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1392104AbiEFMjU (ORCPT ); Fri, 6 May 2022 08:39:20 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A0F6A53A60; Fri, 6 May 2022 05:35:35 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Kvqkq4mTlzfbMj; Fri, 6 May 2022 20:34:27 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 6 May 2022 20:35:33 +0800 Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 6 May 2022 20:35:32 +0800 Subject: Re: [PATCH v23 3/6] arm64: kdump: Reimplement crashkernel=X To: Catalin Marinas CC: Thomas Gleixner , Ingo Molnar , Borislav Petkov , , "H . Peter Anvin" , , Dave Young , Baoquan He , Vivek Goyal , Eric Biederman , , Will Deacon , , Rob Herring , Frank Rowand , , "Jonathan Corbet" , , Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , "John Donnelly" , Dave Kleikamp References: <20220505091845.167-1-thunder.leizhen@huawei.com> <20220505091845.167-4-thunder.leizhen@huawei.com> <189f24a8-9e9b-b3e9-7ac5-935433ea575b@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: Date: Fri, 6 May 2022 20:35:21 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 2022/5/6 19:06, Catalin Marinas wrote: > 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 Er, my idea almost coincides with yours. When 3) removes 'high', it's the same way you think. Of course, I haven't thought of deleting 'high' yet. So your idea is more perfect. > think there's too much bikeshedding already) Yeah, the oldest prince has royal power. There's no choice now. > >>> 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. > -- Regards, Zhen Lei