From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 18 May 2022 09:58:18 +0200 From: Petr Mladek 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: To: "Guilherme G. Piccoli" Cc: David Gow , Evan Green , Julius Werner , Scott Branden , bcm-kernel-feedback-list@broadcom.com, Sebastian Reichel , linux-pm@vger.kernel.org, Florian Fainelli , 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 List-ID: On Tue 2022-05-17 15:57:34, Petr Mladek wrote: > On Mon 2022-05-16 12:06:17, Guilherme G. Piccoli wrote: > > >> --- a/drivers/soc/bcm/brcmstb/pm/pm-arm.c > > >> +++ b/drivers/soc/bcm/brcmstb/pm/pm-arm.c > > >> @@ -814,7 +814,7 @@ static int brcmstb_pm_probe(struct platform_device *pdev) > > >> goto out; > > >> } > > >> > > >> - atomic_notifier_chain_register(&panic_notifier_list, > > >> + atomic_notifier_chain_register(&panic_hypervisor_list, > > >> &brcmstb_pm_panic_nb); > > > > > > I am not sure about this one. It instruct some HW to preserve DRAM. > > > IMHO, it better fits into pre_reboot category but I do not have > > > strong opinion. > > > > 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. As discussed in the other other reply, it seems that both affected notifiers do not store kernel logs and should stay in the "hypervisor". > 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. I just want to point out that the above idea has problems. Notifiers storing kernel log need to be treated as kmsg_dump(). In particular, we would need to know if there are any. We do not need to call "info" notifier list before kdump when there is no kernel log dumper registered. Best Regards, Petr