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 B1E99C4332F for ; Tue, 8 Nov 2022 02:48:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230362AbiKHCru (ORCPT ); Mon, 7 Nov 2022 21:47:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232494AbiKHCrX (ORCPT ); Mon, 7 Nov 2022 21:47:23 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42AA32E9FE; Mon, 7 Nov 2022 18:47:22 -0800 (PST) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4N5svP1nkBzRp3H; Tue, 8 Nov 2022 10:47:13 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 8 Nov 2022 10:47:20 +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 15.1.2375.31; Tue, 8 Nov 2022 10:47:19 +0800 Subject: Re: [PATCH v3 1/2] arm64: kdump: Provide default size when crashkernel=Y,low is not specified To: Catalin Marinas CC: Dave Young , Baoquan He , Vivek Goyal , , , Will Deacon , , Jonathan Corbet , , "Eric W . Biederman" , Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou , John Donnelly , "Dave Kleikamp" References: <20220711090319.1604-1-thunder.leizhen@huawei.com> <20220711090319.1604-2-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <1dd20529-e346-cd64-d93d-54231c8b3d38@huawei.com> Date: Tue, 8 Nov 2022 10:47:18 +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: dggems705-chm.china.huawei.com (10.3.19.182) 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 2022/11/8 1:18, Catalin Marinas wrote: > On Mon, Jul 11, 2022 at 05:03:18PM +0800, Zhen Lei wrote: >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index 2522b11e593f239..65a2c3a22a4b57d 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -843,7 +843,7 @@ >> available. >> It will be ignored if crashkernel=X is specified. >> crashkernel=size[KMG],low >> - [KNL, X86-64] range under 4G. When crashkernel=X,high >> + [KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high >> is passed, kernel could allocate physical memory region >> above 4G, that cause second kernel crash on system >> that require some amount of low memory, e.g. swiotlb >> @@ -857,12 +857,6 @@ >> It will be ignored when crashkernel=X,high is not used >> or memory reserved is below 4G. >> >> - [KNL, ARM64] range in low memory. >> - This one lets the user specify a low range in the >> - DMA zone for the crash dump kernel. >> - It will be ignored when crashkernel=X,high is not used >> - or memory reserved is located in the DMA zones. >> - >> cryptomgr.notests >> [KNL] Disable crypto self-tests >> >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >> index 339ee84e5a61a0b..5390f361208ccf7 100644 >> --- a/arch/arm64/mm/init.c >> +++ b/arch/arm64/mm/init.c >> @@ -96,6 +96,14 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1; >> #define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit >> #define CRASH_ADDR_HIGH_MAX (PHYS_MASK + 1) >> >> +/* >> + * This is an empirical value in x86_64 and taken here directly. Please >> + * refer to the code comment in reserve_crashkernel_low() of x86_64 for more >> + * details. >> + */ >> +#define DEFAULT_CRASH_KERNEL_LOW_SIZE \ >> + max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20) >> + >> static int __init reserve_crashkernel_low(unsigned long long low_size) >> { >> unsigned long long low_base; >> @@ -147,7 +155,9 @@ static void __init reserve_crashkernel(void) >> * is not allowed. >> */ >> ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base); >> - if (ret && (ret != -ENOENT)) >> + if (ret == -ENOENT) >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; >> + else if (ret) >> return; > > BTW, since we want a default low allocation, I think we should change > the checking logic slightly. Currently we have: > > if ((crash_base >= CRASH_ADDR_LOW_MAX) && > crash_low_size && reserve_crashkernel_low(crash_low_size)) { > ... > > If crash_base is just below CRASH_ADDR_LOW_MAX, we deem it sufficient > but a crashkernel trying to allocate 64MB of swiotlb may fail. So maybe > change this to crash_base >= CRASH_ADDR_LOW_MAX - crash_low_size. The equal sign needs to be removed. The situation should be the allocation of "crashkernel=X,high". This possibility is too small, the high memory is unlikely to be that small. memblock_phys_alloc_range() always search for memory block from high addresses to low addresses. In the initial phase, high-end memory is not fragmented. Of course, the modification can make people look more reassuring. OK, I'll update it. > -- Regards, Zhen Lei