From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754694AbbE2IeC (ORCPT ); Fri, 29 May 2015 04:34:02 -0400 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:50650 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754337AbbE2Idx (ORCPT ); Fri, 29 May 2015 04:33:53 -0400 Date: Fri, 29 May 2015 09:33:39 +0100 From: Russell King - ARM Linux To: Hiraku Toyooka Cc: dinguyen@opensource.altera.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available Message-ID: <20150529083339.GG2067@n2100.arm.linux.org.uk> References: <20150529053844.31162.43927.stgit@arietta> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150529053844.31162.43927.stgit@arietta> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 29, 2015 at 02:38:44PM +0900, Hiraku Toyooka wrote: > Kexec_load syscall in ARM checks that machine-specific code > has the smp_ops.cpu_kill() before loading kernel image. > This patch adds the cpu_kill(), as a result, kexec reboot and > kernel crash dump become available in mach-socfpga. Please look at the kexec'd kernel's boot messages. You will probably notice that the kexec'd kernel is unable to start the secondary CPUs, and probably causes them to crash. As socfpga does not appear to be able to do anything with the secondary CPUs other than park them in a WFI loop in the _existing_ kernel, when that existing kernel gets overwritten by the kexec kernel and an interrupt sent to the CPU, that secondary CPU could very well start executing code it's not meant to. So no, this is a bad idea. Unless secondary CPUs can actually be taken offline, features like kexec can't be supported on the platform. -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net.