From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C53FC4167E for ; Wed, 18 May 2022 07:39:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232322AbiERHi7 (ORCPT ); Wed, 18 May 2022 03:38:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232286AbiERHiz (ORCPT ); Wed, 18 May 2022 03:38:55 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46CE31059E0; Wed, 18 May 2022 00:38:54 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id F09A21F9A4; Wed, 18 May 2022 07:38:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1652859533; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+lyyDjAjgyfEhWEBfN0EDdR6Jmx4pHSl+tBKIhX1g7c=; b=j0w4/FD8BT6n50PoBFWZ2B9hxn1McNizrLx3lcvWYTHgmFBxhdJUV3RAv4Ssdii4QSileV Dl88LCOs7NY6Zlry9hleanS5GY4TpOEfeqkhXf/HNSrx5fV+jFGy5YS3+L30Mt6n4dNsLm vyO1S4F65bAw7AbpuXo9HU2OHf85ddo= Received: from suse.cz (unknown [10.100.201.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 5D79B2C142; Wed, 18 May 2022 07:38:52 +0000 (UTC) Date: Wed, 18 May 2022 09:38:52 +0200 From: Petr Mladek To: "Guilherme G. Piccoli" Cc: Scott Branden , Sebastian Reichel , Florian Fainelli , David Gow , Evan Green , Julius Werner , bcm-kernel-feedback-list@broadcom.com, linux-pm@vger.kernel.org, akpm@linux-foundation.org, bhe@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, linux-tegra@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, netdev@vger.kernel.org, openipmi-developer@lists.sourceforge.net, rcu@vger.kernel.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org, Alexander Gordeev , Andrea Parri , Ard Biesheuvel , Benjamin Herrenschmidt , Brian Norris , Christian Borntraeger , Christophe JAILLET , "David S. Miller" , Dexuan Cui , Doug Berger , Haiyang Zhang , Hari Bathini , Heiko Carstens , Justin Chen , "K. Y. Srinivasan" , Lee Jones , Markus Mayer , Michael Ellerman , Mihai Carabas , Nicholas Piggin , Paul Mackerras , Pavel Machek , Shile Zhang , Stephen Hemminger , Sven Schnelle , Thomas Bogendoerfer , Tianyu Lan , Vasily Gorbik , Wang ShaoBo , Wei Liu , zhenwei pi Subject: Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list Message-ID: References: <20220427224924.592546-1-gpiccoli@igalia.com> <20220427224924.592546-20-gpiccoli@igalia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 2022-05-17 13:42:06, Guilherme G. Piccoli wrote: > On 17/05/2022 10:57, Petr Mladek wrote: > >> Disagree here, I'm CCing Florian for information. > >> > >> This notifier preserves RAM so it's *very interesting* if we have > >> kmsg_dump() for example, but maybe might be also relevant in case kdump > >> kernel is configured to store something in a persistent RAM (then, > >> without this notifier, after kdump reboots the system data would be lost). > > > > I see. It is actually similar problem as with > > drivers/firmware/google/gsmi.c. > > > > I does similar things like kmsg_dump() so it should be called in > > the same location (after info notifier list and before kdump). > > > > A solution might be to put it at these notifiers at the very > > end of the "info" list or make extra "dump" notifier list. > > Here I still disagree. I've commented in the other response thread > (about Google gsmi) about the semantics of the hypervisor list, but > again: this list should contain callbacks that > > (a) Should run early, _by default_ before a kdump; > (b) Communicate with the firmware/hypervisor in a "low-risk" way; > > Imagine a scenario where users configure kdump kernel to save something > in a persistent form in DRAM - it'd be like a late pstore, in the next > kernel. This callback enables that, it's meant to inform FW "hey, panic > happened, please from now on don't clear the RAM in the next FW-reboot". > I don't see a reason to postpone that - let's see if the maintainers > have an opinion. I have answered this in more detail in the other reply, see https://lore.kernel.org/r/YoShZVYNAdvvjb7z@alley I agree that both notifiers in drivers/soc/bcm/brcmstb/pm/pm-arm.c drivers/firmware/google/gsmi.c better fit into the hypervisor list after all. Best Regards, Petr