linux-kernel - Re: [PATCH v1 0/3] allow ramoops to collect all kmesg

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Message-ID: <202005041112.F3C8117F67@keescook>
Date:   Mon, 4 May 2020 11:14:28 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     jmorris@...ei.org, sashal@...nel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, sergey.senozhatsky@...il.com,
        rostedt@...dmis.org, anton@...msg.org, ccross@...roid.com,
        tony.luck@...el.com, robh+dt@...nel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v1 0/3] allow ramoops to collect all kmesg_dump events

On Sat, May 02, 2020 at 10:35:52AM -0400, Pavel Tatashin wrote:
> Currently, ramoops is capable to collect dmesg buffer only during
> panic and oops events. However, it is desirable for shutdown performance
> analysis reasons to optionally allow collecting dmesg buffers during other
> events as well: reboot, kexec, emergency reboot etc.
> 
> How to quickly test:
> 
> virtme-run --mods=auto --kdir --mods=auto --kdir . \
> 	-a memmap=1G$8G -a ramoops.mem_address=0x200000000 \
> 	-a ramoops.mem_size=0x100000 -a ramoops.record_size=32768 \
> 	-a ramoops.dump_all=1 -a quiet --qemu-opts -m 8G
> ..
> # reboot -f
> 
> After VM is back:
> 
> # mount -t pstore pstore /mnt
> # head /mnt/dmesg-ramoops-0 
> Restart#1 Part1

Is there a reason that using ramoops.console_size isn't sufficient for
this?

I'm not strictly opposed to making these changes, but traditionally the
granularity of dmesg output has been pretty easily "all or crashes"
instead of a range within.

-- 
Kees Cook