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Peter Anvin" , linux-kernel@vger.kernel.org, Dave Young , Baoquan He , 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 Cc: Randy Dunlap , Feng Zhou , Kefeng Wang , Chen Zhou References: <20220227030717.1464-1-thunder.leizhen@huawei.com> <20220227030717.1464-4-thunder.leizhen@huawei.com> From: Dave Kleikamp In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SN7PR04CA0176.namprd04.prod.outlook.com (2603:10b6:806:125::31) To SJ0PR10MB5742.namprd10.prod.outlook.com (2603:10b6:a03:3ed::20) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: acde4f42-0a05-482f-c5ce-08da0b4466ae X-MS-TrafficTypeDiagnostic: SA2PR10MB4714:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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We use crashkernel=X to reserve crashkernel below 4G, which >> will fail when there is no enough low memory. > >                         " Not enough " >> 2. If reserving crashkernel above 4G, in this case, crash dump >> kernel will boot failure because there is no low memory available >> for allocation. > >  We can't have a "boot failure". If the requested reservation >  can not be met,  the kdump  configuration is not setup. I think you misread this. Without these patches, if only high memory is reserved for the crash kernel, then the crash kernel will fail to boot. >> >> 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. > > Is there going to be documentation on what values certain Arm platforms > are going to use this on ? > >> >> Signed-off-by: Chen Zhou >> Co-developed-by: Zhen Lei >> Signed-off-by: Zhen Lei