[PATCH v2] pstore: add a KHO backend

[Mike Rapoport]

Hi,

On Fri, Jun 05, 2026 at 02:10:40PM +0200, Michal Clapinski wrote:
> Up to this point to preserve late shutdown logs in memory, users had to
> predefine a memory region using ramoops. This commit changes this by
> preserving a buffer using kexec-handover.
> 
> pstore_kho supports preserving only 1 dmesg buffer.
> It gets replaced with the new buffer on every kexec, so the user has to
> copy the file out of pstore after every kexec.
> There is no erase() support.

Sorry I didn't jump at v1.

pstore does not really need a KHO backend. It can use ram backend with
reserve_mem and reserve_mem can be preserved with KHO already.
 
> Signed-off-by: Michal Clapinski <mclapinski at google.com>
> ---
> v2:
> - Added a comment explaining the benefits of pstore_kho.
> - Created include/linux/kho/abi/pstore.h.
> - Got rid of the KHO subtree.
> - Made sure never to free incoming kho data.
>   This way the module can be safely reloaded.
> - Sashiko complained that I trust the data coming from the old kernel.
>   I ignored it. LMK if I shouldn't trust the old kernel.
> ---
>  fs/pstore/Kconfig              |  10 ++
>  fs/pstore/Makefile             |   2 +
>  fs/pstore/pstore_kho.c         | 230 +++++++++++++++++++++++++++++++++
>  include/linux/kho/abi/pstore.h |  27 ++++
>  4 files changed, 269 insertions(+)
>  create mode 100644 fs/pstore/pstore_kho.c
>  create mode 100644 include/linux/kho/abi/pstore.h

-- 
Sincerely yours,
Mike.