Thread (173 messages) 173 messages, 28 authors, 2022-05-24

[PATCH 19/30] panic: Add the panic hypervisor notifier list

From: Petr Mladek <pmladek@suse.com>
Date: 2022-05-18 08:00:03
Also in: linux-alpha, linux-edac, linux-hyperv, linux-leds, linux-mips, linux-pm, linux-remoteproc, linux-s390, linux-tegra, linux-um, linuxppc-dev, lkml, netdev, rcu, sparclinux, xen-devel

On Tue 2022-05-17 15:57:34, Petr Mladek wrote:
On Mon 2022-05-16 12:06:17, Guilherme G. Piccoli wrote:
quoted
quoted
quoted
--- 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
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