Re: [RFC v2 PATCH] reserve_mem: add support for static memory

[Mike Rapoport <rppt@kernel.org>]

On Thu, Jun 18, 2026 at 11:23:31PM -0700, Shyam Saini wrote:
> reserve_mem relies on dynamic memory allocation, this limits the
> usecase where memory is required to be preserved across the boots.
> Eg: ramoops memory reservation on ACPI platforms
>
> So add support to pass a pre-determined static address and reserve
> memory at a specified location. This enables use case like ramoops
> on ACPI platforms to reliably access ramoops region with previous
> boot logs.
> 
> Also skip the parsing of <align> when static address is passed.
> 
> Example syntax for static address
>  reserve_mem=4M@0x1E0000000:oops

reserve_mem is best effort by design because such hacks as well as memmap=
cannot guarantee this memory is actually free.

If you want to preserve ramoops reliably, use KHO with reserve_mem.
The first kernel will allocate memory, this memory will be preserved by KHO
and could be picked up by the second kernel.
 
> Signed-off-by: Shyam Saini <shyamsaini@linux.microsoft.com>
> ---
> v1: https://lore.kernel.org/lkml/0eaf3be2-5121-48b7-aeed-196405c0a480@infradead.org/
> v2: Fix code logic and incorporate Randy's suggestion
> ---
>  .../admin-guide/kernel-parameters.txt         | 15 ++++++
>  mm/memblock.c                                 | 47 +++++++++++++------
>  2 files changed, 47 insertions(+), 15 deletions(-)

-- 
Sincerely yours,
Mike.