From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-pf0-x231.google.com ([2607:f8b0:400e:c00::231]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bKxs2-0007Aw-LI for kexec@lists.infradead.org; Thu, 07 Jul 2016 01:12:51 +0000 Received: by mail-pf0-x231.google.com with SMTP id c2so1139881pfa.2 for ; Wed, 06 Jul 2016 18:12:30 -0700 (PDT) Date: Thu, 7 Jul 2016 10:17:47 +0900 From: AKASHI Takahiro Subject: Re: [PATCH v21 1/8] arm64: kdump: reserve memory for crash dump kernel Message-ID: <20160707011745.GX20774@linaro.org> References: <20160706075226.27609-1-takahiro.akashi@linaro.org> <20160706075226.27609-2-takahiro.akashi@linaro.org> <2543175.KeBui093Sr@hactar> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2543175.KeBui093Sr@hactar> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Thiago Jung Bauermann Cc: Pratyush Anand , geoff@infradead.org, catalin.marinas@arm.com, kexec@lists.infradead.org, will.deacon@arm.com, james.morse@arm.com, Mark Salter , linux-arm-kernel@lists.infradead.org On Wed, Jul 06, 2016 at 03:11:45PM -0300, Thiago Jung Bauermann wrote: > Am Mittwoch, 06 Juli 2016, 16:52:19 schrieb AKASHI Takahiro: > > On the startup of primary kernel, the memory region used by crash dump > > kernel must be specified by "crashkernel=" kernel parameter. > > reserve_crashkernel() will allocate and reserve the region for later use. > > > > User space tools, like kexec-tools, will be able to find that region > > marked as "Crash kernel" in /proc/iomem. > > On powerpc, userspace tools get everything from the device tree (exposed to > userspace in /proc/device-tree/), not /proc/iomem. I started my kdump patches with arm (not arm64) implementation, and so /proc/iomem is used for consistency. Since my kexec-tools (for arm64) have to access /proc/iomem to identify usable memory regions on *UEFI* systems anyway, I didn't think it was odd. (Please note that UEFI won't expose memory regions information via a device tree, but via ACPI table.) > In the case of the crashkernel reserved region, that information is in > /chosen/linux,crashkernel-base and /chosen/linux,crashkernel-size. > > Either way is fine I think. I'm just mentioning this for reference in case > you want the ARM implementation to be closer to another arch which is also > based on the device tree. Adding those properties to a device tree is quite easy (and it won't conflict with /proc/iomem), so I'd like to defer to arm64 maintainers. Thanks, -Takahiro AKASHI > -- > []'s > Thiago Jung Bauermann > IBM Linux Technology Center > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec