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[209.85.220.65]) by mx.google.com with SMTPS id 38sor39518916pln.23.2019.04.08.22.20.25 for (Google Transport Security); Mon, 08 Apr 2019 22:20:25 -0700 (PDT) Received-SPF: pass (google.com: domain of bhsharma@redhat.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of bhsharma@redhat.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=bhsharma@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Google-Smtp-Source: APXvYqzhrg94zZKMqARZTPlnpBF65FbExNLYEDlH8PaVsNnFFrNS5x/xA9UeSdVBUIhP+KvcD/Laog== X-Received: by 2002:a17:902:b715:: with SMTP id d21mr35489861pls.103.1554787224724; Mon, 08 Apr 2019 22:20:24 -0700 (PDT) Received: from localhost.localdomain ([209.132.188.81]) by smtp.gmail.com with ESMTPSA id y19sm43192451pfn.164.2019.04.08.22.20.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Apr 2019 22:20:23 -0700 (PDT) Subject: Re: [PATCH 0/3] support reserving crashkernel above 4G on arm64 kdump To: Chen Zhou , catalin.marinas@arm.com, will.deacon@arm.com, akpm@linux-foundation.org, rppt@linux.ibm.com, ard.biesheuvel@linaro.org, takahiro.akashi@linaro.org Cc: wangkefeng.wang@huawei.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org References: <20190403030546.23718-1-chenzhou10@huawei.com> From: Bhupesh Sharma Message-ID: <49012d55-2020-e2ac-1102-59a5f3911a29@redhat.com> Date: Tue, 9 Apr 2019 13:20:16 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20190403030546.23718-1-chenzhou10@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Chen, Thanks for the patchset. Before I review the patches in detail, I have a couple of generic queries. Please see them in-line: On 04/03/2019 11:05 AM, Chen Zhou wrote: > When crashkernel is reserved above 4G in memory, kernel should reserve > some amount of low memory for swiotlb and some DMA buffers. So there may > be two crash kernel regions, one is below 4G, the other is above 4G. > > Crash dump kernel reads more than one crash kernel regions via a dtb > property under node /chosen, > linux,usable-memory-range = . > > Besides, we need to modify kexec-tools: > arm64: support more than one crash kernel regions > > Chen Zhou (3): > arm64: kdump: support reserving crashkernel above 4G > arm64: kdump: support more than one crash kernel regions > kdump: update Documentation about crashkernel on arm64 > > Documentation/admin-guide/kernel-parameters.txt | 4 +- > arch/arm64/kernel/setup.c | 3 + > arch/arm64/mm/init.c | 108 ++++++++++++++++++++---- > include/linux/memblock.h | 1 + > mm/memblock.c | 40 +++++++++ > 5 files changed, 139 insertions(+), 17 deletions(-) I am wondering about the use-case for the same. I remember normally fedora-based arm64 systems can do well with a maximum crashkernel size of <=512MB reserved below the 4G boundary. So, do you mean that for your use-case (may be a huawei board based setup?), you need: - more than 512MB of crashkernel size, or - you want to split the crashkernel reservation across the 4GB boundary irrespective of the crashkernel size value. Thanks, Bhupesh