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

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