[PATCH v2] pstore: add a KHO backend

[Pasha Tatashin]

On 06-12 17:42, Mike Rapoport wrote:
> 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.

I just tested it, and it works well, I think it would be fine for 
Google's requirements:

CONFIG_PSTORE=y
CONFIG_PSTORE_RAM=y
CONFIG_PSTORE_CONSOLE=y

With the following parameters:
'reserve_mem=2M:2M:dmesg_buffer ramoops.mem_name=dmesg_buffer ramoops.max_reason=5 ramoops.console_size=2097152 ramoops.record_size=0 ramoops.ftrace_size=0 ramoops.pmsg_size=0'

KHO preserves pstore properly. However, we need one patch that would 
allow for ramoops console to capture the output even when quiet is 
provided.

Pasha