From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pa0-x231.google.com ([2607:f8b0:400e:c03::231]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Zp7Vn-0002aA-Sd for kexec@lists.infradead.org; Thu, 22 Oct 2015 04:30:01 +0000 Received: by pabrc13 with SMTP id rc13so75133108pab.0 for ; Wed, 21 Oct 2015 21:29:38 -0700 (PDT) Subject: Re: [PATCH 13/16] arm64: kdump: add kdump support References: <20151022032534.GC11227@dhcp-129-115.nay.redhat.com> From: AKASHI Takahiro Message-ID: <5628662B.1020605@linaro.org> Date: Thu, 22 Oct 2015 13:29:31 +0900 MIME-Version: 1.0 In-Reply-To: <20151022032534.GC11227@dhcp-129-115.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: Dave Young , Geoff Levand Cc: Mark Rutland , AKASHI@infradead.org, marc.zyngier@arm.com, Catalin Marinas , Will Deacon , christoffer.dall@linaro.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org Hi Dave, Thank you for your comment. On 10/22/2015 12:25 PM, Dave Young wrote: > Hi, AKASHI, > > On 10/19/15 at 11:38pm, Geoff Levand wrote: >> From: AKASHI Takahiro >> >> On crash dump kernel, all the information about primary kernel's core >> image is available in elf core header specified by "elfcorehdr=" boot >> parameter. reserve_elfcorehdr() will set aside the region to avoid any >> corruption by crash dump kernel. >> >> Crash dump kernel will access the system memory of primary kernel via >> copy_oldmem_page(), which reads one page by ioremap'ing it since it does >> not reside in linear mapping on crash dump kernel. >> Please note that we should add "mem=X[MG]" boot parameter to limit the >> memory size and avoid the following assertion at ioremap(): >> if (WARN_ON(pfn_valid(__phys_to_pfn(phys_addr)))) >> return NULL; >> when accessing any pages beyond the usable memories of crash dump kernel. > > How does kexec-tools pass usable memory ranges to kernel? using dtb? > Passing an extra mem=X sounds odd in the design. Kdump kernel should get > usable ranges and hanle the limit better than depending on an extern kernel > param. Well, regarding "depending on an external kernel param," - this limitation ("mem=") is compatible with arm(32) implementation although it is not clearly described in kernel's Documentation/kdump/kdump.txt. - "elfcorehdr" kernel parameter is mandatory on x86 as well as on arm/arm64. The parameter is explicitly generated and added by kexec-tools. Do I miss your point? Thanks, -Takahiro AKASHI > Thanks > Dave > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec