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 X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2872C433E6 for ; Wed, 24 Feb 2021 16:10:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B69C364EFA for ; Wed, 24 Feb 2021 16:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234302AbhBXQJt (ORCPT ); Wed, 24 Feb 2021 11:09:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:57924 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234059AbhBXQFF (ORCPT ); Wed, 24 Feb 2021 11:05:05 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 77C4264E6C; Wed, 24 Feb 2021 16:04:11 +0000 (UTC) Date: Wed, 24 Feb 2021 16:04:08 +0000 From: Catalin Marinas To: Chen Zhou Cc: mingo@redhat.com, tglx@linutronix.de, rppt@kernel.org, dyoung@redhat.com, bhe@redhat.com, will@kernel.org, nsaenzjulienne@suse.de, corbet@lwn.net, John.P.donnelly@oracle.com, bhsharma@redhat.com, prabhakar.pkin@gmail.com, horms@verge.net.au, robh+dt@kernel.org, arnd@arndb.de, james.morse@arm.com, xiexiuqi@huawei.com, guohanjun@huawei.com, huawei.libin@huawei.com, wangkefeng.wang@huawei.com, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [PATCH v14 08/11] arm64: kdump: reimplement crashkernel=X Message-ID: <20210224160408.GC28965@arm.com> References: <20210130071025.65258-1-chenzhou10@huawei.com> <20210130071025.65258-9-chenzhou10@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210130071025.65258-9-chenzhou10@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 30, 2021 at 03:10:22PM +0800, Chen Zhou wrote: > There are following issues in arm64 kdump: > 1. We use crashkernel=X to reserve crashkernel below 4G, which > will fail when there is no enough low memory. > 2. If reserving crashkernel above 4G, in this case, crash dump > kernel will boot failure because there is no low memory available > for allocation. > > To solve these issues, change the behavior of crashkernel=X and > introduce crashkernel=X,[high,low]. crashkernel=X tries low allocation > in DMA zone, and fall back to high allocation if it fails. > We can also use "crashkernel=X,high" to select a region above DMA zone, > which also tries to allocate at least 256M in DMA zone automatically. > "crashkernel=Y,low" can be used to allocate specified size low memory. > > Another minor change, there may be two regions reserved for crash > dump kernel, in order to distinct from the high region and make no > effect to the use of existing kexec-tools, rename the low region as > "Crash kernel (low)". I think we discussed this but I don't remember the conclusion. Is this only renamed conditionally so that we don't break current kexec-tools? IOW, assuming that the full crashkernel region is reserved below 4GB, does the "(low)" suffix still appear or it's only if a high region is additionally reserved? > diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h > index 3f6ecae0bc68..f0caed0cb5e1 100644 > --- a/arch/arm64/include/asm/kexec.h > +++ b/arch/arm64/include/asm/kexec.h > @@ -96,6 +96,10 @@ static inline void crash_prepare_suspend(void) {} > static inline void crash_post_resume(void) {} > #endif > > +#ifdef CONFIG_KEXEC_CORE > +extern void __init reserve_crashkernel(void); > +#endif Why not have this in some generic header? > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c > index c18aacde8bb0..69c592c546de 100644 > --- a/arch/arm64/kernel/setup.c > +++ b/arch/arm64/kernel/setup.c > @@ -238,7 +238,18 @@ static void __init request_standard_resources(void) > kernel_data.end <= res->end) > request_resource(res, &kernel_data); > #ifdef CONFIG_KEXEC_CORE > - /* Userspace will find "Crash kernel" region in /proc/iomem. */ > + /* > + * Userspace will find "Crash kernel" or "Crash kernel (low)" > + * region in /proc/iomem. > + * In order to distinct from the high region and make no effect > + * to the use of existing kexec-tools, rename the low region as > + * "Crash kernel (low)". > + */ > + if (crashk_low_res.end && crashk_low_res.start >= res->start && > + crashk_low_res.end <= res->end) { > + crashk_low_res.name = "Crash kernel (low)"; > + request_resource(res, &crashk_low_res); > + } > if (crashk_res.end && crashk_res.start >= res->start && > crashk_res.end <= res->end) > request_resource(res, &crashk_res); My reading of the new generic reserve_crashkernel() is that crashk_low_res will only be populated if crask_res is above 4GB. If that's correct, I'm fine with the renaming here since current systems would not get a renamed low reservation (as long as they don't change the kernel cmdline). > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 912f64f505f7..d20f5c444ebf 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -35,6 +35,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -61,66 +62,11 @@ EXPORT_SYMBOL(memstart_addr); > */ > phys_addr_t arm64_dma_phys_limit __ro_after_init; > > -#ifdef CONFIG_KEXEC_CORE > -/* > - * reserve_crashkernel() - reserves memory for crash kernel > - * > - * This function reserves memory area given in "crashkernel=" kernel command > - * line parameter. The memory reserved is used by dump capture kernel when > - * primary kernel is crashing. > - */ > +#ifndef CONFIG_KEXEC_CORE > static void __init reserve_crashkernel(void) > { [...] > } > +#endif Can we not have the dummy reserve_crashkernel() in the generic code as well and avoid the #ifndef here? > #ifdef CONFIG_CRASH_DUMP > static int __init early_init_dt_scan_elfcorehdr(unsigned long node, > @@ -446,6 +392,14 @@ void __init bootmem_init(void) > * reserved, so do it here. > */ > reserve_crashkernel(); > +#ifdef CONFIG_KEXEC_CORE > + /* > + * The low region is intended to be used for crash dump kernel devices, > + * just mark the low region as "nomap" simply. > + */ > + if (crashk_low_res.end) > + memblock_mark_nomap(crashk_low_res.start, resource_size(&crashk_low_res)); > +#endif Do we do something similar for crashk_res? Also, I can see we call crash_exclude_mem_range() only for crashk_res. Do we need to do this for crashk_low_res as well? -- Catalin