Re: [PATCH v4 2/2] mm/memblock: Add reserve_mem debugfs info

[SeongJae Park <sj@kernel.org>]

On Mon, 23 Mar 2026 22:22:18 -0300 "Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:

> When using the "reserve_mem" parameter, users aim at having an
> area that (hopefully) persists across boots, so pstore infrastructure
> (like ramoops module) can make use of that to save oops/ftrace logs,
> for example.
> 
> There is no easy way to determine if this kernel parameter is properly
> set though; the kernel doesn't show information about this memory in
> memblock debugfs, neither in /proc/iomem nor dmesg. This is a relevant
> information for tools like kdumpst[0], to determine if it's reliable
> to use the reserved area as ramoops persistent storage; checking only
> /proc/cmdline is not sufficient as it doesn't tell if the reservation
> effectively succeeded or not.
> 
> Add here a new file under memblock debugfs showing properly set memory
> reservations, with name and size as passed to "reserve_mem". Notice that
> if no "reserve_mem=" is passed on command-line or if the reservation
> attempts fail, the file is not created.
> 
> [0] https://aur.archlinux.org/packages/kdumpst
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: SeongJae Park <sj@kernel.org>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>

Reviewed-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

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