From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752880AbdHDNbb (ORCPT ); Fri, 4 Aug 2017 09:31:31 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:35140 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752448AbdHDNba (ORCPT ); Fri, 4 Aug 2017 09:31:30 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] arm64:kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores From: Hoeun Ryu X-Mailer: iPhone Mail (14F89) In-Reply-To: <59844E98.3020507@arm.com> Date: Fri, 4 Aug 2017 22:31:26 +0900 Cc: Catalin Marinas , Will Deacon , AKASHI Takahiro , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-Id: <31F08185-69F6-4EB9-92B0-A8C6DD6B7532@gmail.com> References: <1501830173-15989-1-git-send-email-hoeun.ryu@gmail.com> <59844E98.3020507@arm.com> To: James Morse Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v74DVaQa007437 > On 4 Aug 2017, at 7:38 PM, James Morse wrote: > > Hi Hoeun, > >> On 04/08/17 08:02, Hoeun Ryu wrote: >> Commit 0ee5941 : (x86/panic: replace smp_send_stop() with kdump friendly >> version in panic path) introduced crash_smp_send_stop() which is a weak >> function and can be overriden by architecture codes to fix the side effect >> caused by commit f06e515 : (kernel/panic.c: add "crash_kexec_post_ >> notifiers" option). > > If I've understood correctly: if we boot with this option core code doesn't use > our machine_crash_shutdown(), and instead calls crash_smp_send_stop(), which we > don't have, so it uses the default smp_send_stop(), which doesn't save the regs. > > Thanks for catching this! > > > Could we rename smp_send_crash_stop() crash_smp_send_stop() and add the > called-twice logic there? They are similar enough that I'm getting them muddled > already! I think it is possible, I will reflect it in v2. Thank you for the review. > > Thanks, > > James > > >> ARM64 architecture uses the weak version function and the problem is that >> the weak function simply calls smp_send_stop() which makes other CPUs >> offline and takes away the chance to save crash information for nonpanic >> CPUs in machine_crash_shutdown() when crash_kexec_post_notifiers kernel >> option is enabled. >> >> Calling smp_send_crash_stop() in the function is useless because all >> nonpanic CPUs are already offline by smp_send_stop() in this case and >> smp_send_crash_stop() only works against online CPUs. >> >> The result is that /proc/vmcore is not available with the error messages; >> "Warning: Zero PT_NOTE entries found", "Kdump: vmcore not initialized". >> >> crash_smp_send_stop() is implemented for ARM64 architecture to fix this >> problem and the function (strong symbol version) saves crash information >> for nonpanic CPUs using smp_send_crash_stop() and machine_crash_shutdown() >> tries to save crash information for nonpanic CPUs only when >> crash_kexec_post_notifiers kernel option is disabled. > >