From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pd0-f180.google.com ([209.85.192.180]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Ys4gg-0005Uk-Dr for kexec@lists.infradead.org; Tue, 12 May 2015 07:33:10 +0000 Received: by pdbnk13 with SMTP id nk13so173638918pdb.0 for ; Tue, 12 May 2015 00:32:48 -0700 (PDT) Message-ID: <5551AC97.9040802@linaro.org> Date: Tue, 12 May 2015 16:32:39 +0900 From: AKASHI Takahiro MIME-Version: 1.0 Subject: Re: [v2 1/5] arm64: kdump: reserve memory for crash dump kernel References: <1429861989-8417-1-git-send-email-takahiro.akashi@linaro.org> <1429861989-8417-2-git-send-email-takahiro.akashi@linaro.org> <20150428091935.GJ15033@dhcp-16-116.nay.redhat.com> <55505C91.8070503@linaro.org> <20150511075447.GA4290@dhcp-128-28.nay.redhat.com> <5550659D.90006@linaro.org> <20150511094115.GB4290@dhcp-128-28.nay.redhat.com> In-Reply-To: <20150511094115.GB4290@dhcp-128-28.nay.redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He Cc: hbabus@us.ibm.com, linaro-kernel@lists.linaro.org, geoff@infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, vgoyal@redhat.com, broonie@kernel.org, david.griego@linaro.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org On 05/11/2015 06:41 PM, Baoquan He wrote: > On 05/11/15 at 05:17pm, AKASHI Takahiro wrote: >> On 05/11/2015 04:54 PM, Baoquan He wrote: >>> In this patch you reserve a separate memory region in 1st kernel to >>> store elfcorehdr. I am wondering why you don't call add_buffer in >>> kexec-tools directly. Like this you can get a region from reserved >>> crashkernel region. Then you don't need reserve_elfcorehdr() to reserve >>> memory for elfcorehdr specifically. Like other ARCHs do only one memory >>> region is reserved in 1st kernel, that's crashkernel region. >> >> I think that you misunderstand somewhat. >> * Kexec-tools only locates/identifies a small region for elfcore header within crash kernel's >> memory region while 1st kernel is running. >> * the data in elfcore header is filled up by kexec_load system call on 1st kernel. >> * 1st kernel doesn't reserve any region for elfcore header because the kernel >> commandline parameters don't contains "elfcorehdr=" parameter, then elfcorehdr_size=0. >> * Crash dump kernel does reserve the region, as I said, because we don't want to >> corrupt the info in elfcore header accidentally while crash kernel is running. >> >> Clear? > > OK, got it now. > > Then I am wondering why "elfcorehdr=" can't be contained in kernel > cmdline as other ARCH does. Maybe I need go over all related threads > then know why it is. Thanks for explanation. Kexec-tools on 1st kernel appends "elfcorehdr=" to the kernel command line, actually chosen/bootargs in a device tree, that is passed to *crash dump kernel*. So when crash dump kernel boots up, it can recognizes that area (and reserves it for later use of managing /proc/vmcore.) Thanks, -Takahiro AKASHI > Thanks > Baoquan > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec