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 C729AC433F5 for ; Wed, 16 Feb 2022 10:22:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7/+AsvYveGXSJEL0s6ugrAmve0M1VmuW47+DMyMnnUo=; b=aTDxPA4Q/+AbHb 34TnQ14dQfn/mCXLjpTsy5JNw6UcCslCFLiHMYokIf/99DK5is+ssOy72VPLQmghau+s6mMvoiqwj ipbIJUwgMBVeO4FFResKkl3J/wHTcy7igEKuPmNFcTq1zU69UEx6YTDuPiiiyGQDTI/yTl4Rvxyr+ Ua246DufpbzhDnMITfE5ZwVYWk9C/5JNuJS3Hx71ulu3yHhg/Tvt9IBHklWaHPEABeL5dKT8SxESO gt4d/CE4oi+7MOk4q0dy+xMTk8ZyXFnEDGZRX+IqlLdfI9s9Qeu6aB3VCoY00hCAMJFcOjcfIcmDv L9RTF4zB0YY0wnCcgz5A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nKHR2-006V1c-3U; Wed, 16 Feb 2022 10:21:20 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nKHQx-006UzH-6Q for linux-arm-kernel@lists.infradead.org; Wed, 16 Feb 2022 10:21:17 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645006874; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=sfjiT9hvH+PfPn+X9Vuuf3OiUTodgHii1kaq2hHxdic=; b=ElrgBDY0HJcnzn6DCzTTW2AmQY/b2m0wBoQHdYFPMrKLrVp2hAy7W+Vxx5STdZci0QxTEN +luQTd/kd2k4OHb2d4vfVVxhrYPKrH3SaPhA85J0LTjD1fyTR0qjFaXhoduLIAiKZzjHPh +0/+nXGrpfixz4mb9pnB9flddWxRhjI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-582-j-WaJnkpMUCUO4yvrwpt2A-1; Wed, 16 Feb 2022 05:21:10 -0500 X-MC-Unique: j-WaJnkpMUCUO4yvrwpt2A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A0974814245; Wed, 16 Feb 2022 10:21:06 +0000 (UTC) Received: from localhost (ovpn-13-16.pek2.redhat.com [10.72.13.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B68655E4B6; Wed, 16 Feb 2022 10:21:00 +0000 (UTC) Date: Wed, 16 Feb 2022 18:20:58 +0800 From: Baoquan He To: "Leizhen (ThunderTown)" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org, Dave Young , Vivek Goyal , Eric Biederman , kexec@lists.infradead.org, Catalin Marinas , 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 v20 3/5] arm64: kdump: reimplement crashkernel=X Message-ID: References: <20220124084708.683-1-thunder.leizhen@huawei.com> <20220124084708.683-4-thunder.leizhen@huawei.com> <0e84548b-179a-1bad-8f49-963d66426e43@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220216_022115_462382_02397AB9 X-CRM114-Status: GOOD ( 51.60 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 02/16/22 at 10:58am, Leizhen (ThunderTown) wrote: > > > On 2022/2/14 15:53, Leizhen (ThunderTown) wrote: > > > > > > On 2022/2/14 11:52, Baoquan He wrote: > >> On 01/24/22 at 04:47pm, Zhen Lei wrote: > >> ...... > >>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > >>> index 6c653a2c7cff052..a5d43feac0d7d96 100644 > >>> --- a/arch/arm64/mm/init.c > >>> +++ b/arch/arm64/mm/init.c > >>> @@ -71,6 +71,30 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init; > >>> #define CRASH_ADDR_LOW_MAX arm64_dma_phys_limit > >>> #define CRASH_ADDR_HIGH_MAX MEMBLOCK_ALLOC_ACCESSIBLE > >>> > >>> +static int __init reserve_crashkernel_low(unsigned long long low_size) > >>> +{ > >>> + unsigned long long low_base; > >>> + > >>> + /* passed with crashkernel=0,low ? */ > >>> + if (!low_size) > >>> + return 0; > >>> + > >>> + low_base = memblock_phys_alloc_range(low_size, CRASH_ALIGN, 0, CRASH_ADDR_LOW_MAX); > >>> + if (!low_base) { > >>> + pr_err("cannot allocate crashkernel low memory (size:0x%llx).\n", low_size); > >>> + return -ENOMEM; > >>> + } > >>> + > >>> + pr_info("crashkernel low memory reserved: 0x%llx - 0x%llx (%lld MB)\n", > >>> + low_base, low_base + low_size, low_size >> 20); > >>> + > >>> + crashk_low_res.start = low_base; > >>> + crashk_low_res.end = low_base + low_size - 1; > >>> + insert_resource(&iomem_resource, &crashk_low_res); > >>> + > >>> + return 0; > >>> +} > >>> + > >>> /* > >>> * reserve_crashkernel() - reserves memory for crash kernel > >> > >> My another concern is the crashkernel=,low handling. In this patch, the > >> code related to low memory is obscure. Wondering if we should make them > >> explicit with a little redundant but very clear code flows. Saying this > >> because the code must be very clear to you and reviewers, it may be > >> harder for later code reader or anyone interested to understand. > >> > >> 1) crashkernel=X,high > >> 2) crashkernel=X,high crashkernel=Y,low > >> 3) crashkernel=X,high crashkernel=0,low > >> 4) crashkernel=X,high crashkernel='messy code',low > >> 5) crashkernel=X //fall back to high memory, low memory is required then. > >> > >> It could be me thinking about it too much. I made changes to your patch > >> with a tuning, not sure if it's OK to you. Otherwise, this patchset > > > > I think it's good. > > > >> works very well for all above test cases, it's ripe to be merged for > >> wider testing. > > > > I will test it tomorrow. I've prepared a little more use cases than yours. > > After the following modifications, I have tested it and it works well. Passed > all the test cases I prepared. That's great. You might need to add 'crashkernel=xM, crashkernel=0,low', 'crashkernel=xM, crashkernel='messy code',low' to your test cases. > > > > > 1) crashkernel=4G //high=4G, low=256M > > 2) crashkernel=4G crashkernel=512M,high crashkernel=512M,low //high=4G, low=256M, high and low are ignored > > 3) crashkernel=4G crashkernel=512M,high //high=4G, low=256M, high is ignored > > 4) crashkernel=4G crashkernel=512M,low //high=4G, low=256M, low is ignored > > 5) crashkernel=4G@0xe0000000 //high=0G, low=0M, cannot allocate, failed > > 6) crashkernel=512M //high=0G, low=512M > > 7) crashkernel=128M //high=0G, low=128M > > 8) crashkernel=512M@0xde000000 //512M@3552M //high=0G, low=512M > > 9) crashkernel=4G,high //high=4G, low=256M > > a) crashkernel=4G,high crashkernel=512M,low //high=4G, low=512M > > b) crashkernel=512M,high crashkernel=128M,low //high=512M, low=128M > > c) crashkernel=512M,low //high=0G, low=0M, invalid > > > > > >> > >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > >> index a5d43feac0d7..671862c56d7d 100644 > >> --- a/arch/arm64/mm/init.c > >> +++ b/arch/arm64/mm/init.c > >> @@ -94,7 +94,8 @@ static int __init reserve_crashkernel_low(unsigned long long low_size) > >> > >> return 0; > >> } > >> - > >> +/*Words explaining why it's 256M*/ > >> +#define DEFAULT_CRASH_KERNEL_LOW_SIZE SZ_256M > > It's an empirical value. > > 94fb9334182284e8e7e4bcb9125c25dc33af19d4 x86/crash: Allocate enough low memory when crashkernel=high > > When the crash kernel is loaded above 4GiB in memory, the > first kernel allocates only 72MiB of low-memory for the DMA > requirements of the second kernel. On systems with many > devices this is not enough and causes device driver > initialization errors and failed crash dumps. Testing by > SUSE and Redhat has shown that 256MiB is a good default > value for now and the discussion has lead to this value as > well. So set this default value to 256MiB to make sure there > is enough memory available for DMA. Then, some words like below can be added. I am not confident it's good enought, hope someone else can help to polish it. /* * This is an empirical value in x86_64 and taken here directly. Please * refer to code comment in reserve_crashkernel_low() of x86_64 for more * details. */ #define DEFAULT_CRASH_KERNEL_LOW_SIZE SZ_256M > > > >> /* > >> * reserve_crashkernel() - reserves memory for crash kernel > >> * > >> @@ -105,10 +106,10 @@ static int __init reserve_crashkernel_low(unsigned long long low_size) > >> static void __init reserve_crashkernel(void) > >> { > >> unsigned long long crash_base, crash_size; > >> - unsigned long long crash_low_size = SZ_256M; > >> + unsigned long long crash_low_size; > >> unsigned long long crash_max = CRASH_ADDR_LOW_MAX; > >> int ret; > >> - bool fixed_base; > >> + bool fixed_base, high; > > high = false; > > >> char *cmdline = boot_command_line; > >> > >> /* crashkernel=X[@offset] */ > >> @@ -126,7 +127,10 @@ static void __init reserve_crashkernel(void) > >> ret = parse_crashkernel_low(cmdline, 0, &low_size, &crash_base); > >> if (!ret) > >> crash_low_size = low_size; > >> + else > >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; > >> > >> + high = true; > >> crash_max = CRASH_ADDR_HIGH_MAX; > >> } > >> > >> @@ -134,7 +138,7 @@ static void __init reserve_crashkernel(void) > >> crash_size = PAGE_ALIGN(crash_size); > >> > >> /* User specifies base address explicitly. */ > >> - if (crash_base) > >> + if (fixed_base) > >> crash_max = crash_base + crash_size; > >> > >> retry: > >> @@ -156,7 +160,10 @@ static void __init reserve_crashkernel(void) > >> return; > >> } > >> > >> - if (crash_base >= SZ_4G && reserve_crashkernel_low(crash_low_size)) { > >> + if (crash_base >= SZ_4G && !high) > >> + crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; > >> + > >> + if (reserve_crashkernel_low(crash_low_size)) { > >> memblock_phys_free(crash_base, crash_size); > >> return; > >> } > > - if (crash_base >= SZ_4G && reserve_crashkernel_low(crash_low_size)) { > - memblock_phys_free(crash_base, crash_size); > - return; > + if (crash_base >= SZ_4G) { > + if (!high) > + crash_low_size = SZ_256M; > + > + if (reserve_crashkernel_low(crash_low_size)) { > + memblock_phys_free(crash_base, crash_size); > + return; > + } > } > > Looks like changing 'high' to 'low' would be more accurate. Whether crashkernel=Y,low is specified. What I menat is like below, we even can add code comment to make it more clearer. static void __init reserve_crashkernel(void) { /* crashkernel=X[@offset] */ ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), &crash_size, &crash_base); if (ret || !crash_size) { unsigned long long low_size; /* crashkernel=X,high */ ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); if (ret || !crash_size) return; /* crashkernel=X,low */ ret = parse_crashkernel_low(cmdline, 0, &low_size, &crash_base); //case #1, crashkernel=yM,low is specified explicitly in cmdline if (!ret) crash_low_size = low_size; else //case #2, crashkernel=yM,low is not specified explicitly crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; //high means crashkernel,high is specified explicitly high = true; crash_max = CRASH_ADDR_HIGH_MAX; } fixed_base = !!crash_base; crash_size = PAGE_ALIGN(crash_size); /* User specifies base address explicitly. */ if (crash_base) crash_max = crash_base + crash_size; retry: crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, crash_base, crash_max); if (!crash_base) { /* * Attempt to fully allocate low memory failed, fall back * to high memory, the minimum required low memory will be * reserved later. */ if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { crash_max = CRASH_ADDR_HIGH_MAX; goto retry; } pr_warn("cannot allocate crashkernel (size:0x%llx)\n", crash_size); return; } //case #3: get crashkernel from high memory through fallback, let's set crashkernel,low too. if (crash_base >= SZ_4G && !high) crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE; if (reserve_crashkernel_low(crash_low_size)) { memblock_phys_free(crash_base, crash_size); return; } pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n", crash_base, crash_base + crash_size, crash_size >> 20); /* * The crashkernel memory will be removed from the kernel linear * map. Inform kmemleak so that it won't try to access it. */ kmemleak_ignore_phys(crash_base); if (crashk_low_res.end) kmemleak_ignore_phys(crashk_low_res.start); crashk_res.start = crash_base; crashk_res.end = crash_base + crash_size - 1; insert_resource(&iomem_resource, &crashk_res); } > > > > > > It feels like {} may need to be added here so that it is in branch "if (crash_base >= SZ_4G)". > > The case of "crashkernel=128M" will not fall back to high memory and does not need to reserve > > low memory again. > > > >> > >>> * > >>> @@ -81,29 +105,62 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init; > >>> static void __init reserve_crashkernel(void) > >>> { > >>> unsigned long long crash_base, crash_size; > >>> + unsigned long long crash_low_size = SZ_256M; > >>> unsigned long long crash_max = CRASH_ADDR_LOW_MAX; > >>> int ret; > >>> + bool fixed_base; > >>> + char *cmdline = boot_command_line; > >>> > >>> - ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(), > >>> + /* crashkernel=X[@offset] */ > >>> + ret = parse_crashkernel(cmdline, memblock_phys_mem_size(), > >>> &crash_size, &crash_base); > >>> - /* no crashkernel= or invalid value specified */ > >>> - if (ret || !crash_size) > >>> - return; > >>> + if (ret || !crash_size) { > >>> + unsigned long long low_size; > >>> > >>> + /* crashkernel=X,high */ > >>> + ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base); > >>> + if (ret || !crash_size) > >>> + return; > >>> + > >>> + /* crashkernel=X,low */ > >>> + ret = parse_crashkernel_low(cmdline, 0, &low_size, &crash_base); > >>> + if (!ret) > >>> + crash_low_size = low_size; > >>> + > >>> + crash_max = CRASH_ADDR_HIGH_MAX; > >>> + } > >>> + > >>> + fixed_base = !!crash_base; > >>> crash_size = PAGE_ALIGN(crash_size); > >>> > >>> /* User specifies base address explicitly. */ > >>> if (crash_base) > >>> crash_max = crash_base + crash_size; > >>> > >>> +retry: > >>> crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, > >>> crash_base, crash_max); > >>> if (!crash_base) { > >>> + /* > >>> + * Attempt to fully allocate low memory failed, fall back > >>> + * to high memory, the minimum required low memory will be > >>> + * reserved later. > >>> + */ > >>> + if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) { > >>> + crash_max = CRASH_ADDR_HIGH_MAX; > >>> + goto retry; > >>> + } > >>> + > >>> pr_warn("cannot allocate crashkernel (size:0x%llx)\n", > >>> crash_size); > >>> return; > >>> } > >>> > >>> + if (crash_base >= SZ_4G && reserve_crashkernel_low(crash_low_size)) { > >>> + memblock_phys_free(crash_base, crash_size); > >>> + return; > >>> + } > >>> + > >>> pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n", > >>> crash_base, crash_base + crash_size, crash_size >> 20); > >>> > >>> @@ -112,6 +169,9 @@ static void __init reserve_crashkernel(void) > >>> * map. Inform kmemleak so that it won't try to access it. > >>> */ > >>> kmemleak_ignore_phys(crash_base); > >>> + if (crashk_low_res.end) > >>> + kmemleak_ignore_phys(crashk_low_res.start); > >>> + > >>> crashk_res.start = crash_base; > >>> crashk_res.end = crash_base + crash_size - 1; > >>> insert_resource(&iomem_resource, &crashk_res); > >>> -- > >>> 2.25.1 > >>> > >> > >> . > >> > > > > -- > Regards, > Zhen Lei > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel