On Fri, Jun 12, 2026 at 8:38 PM Pasha Tatashin <[email protected]> wrote: > > On 06-12 19:57, Michał Cłapiński wrote: > > On Fri, Jun 12, 2026 at 7:21 PM Pasha Tatashin > > <[email protected]> wrote: > > > > > > 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 > > > > Is it common to write to this console? I think what I typically see in > > the console are error logs that are also in dmesg, so if I preserve > > console logs and dmesg I just have 2 files where one is a subset of > > lines from the other. > > We need either your KHO backend, or the following patch: > https://lore.kernel.org/all/[email protected]/ > > We need all dmesg messages.
We get all of the dmesg messages if you compile with CONFIG_PSTORE=y CONFIG_PSTORE_RAM=y and the cmdline: reserve_mem=2M:2M:dmesg_buffer ramoops.mem_name=dmesg_buffer ramoops.max_reason=5 ramoops.console_size=0 ramoops.record_size=2097152 ramoops.ftrace_size=0 ramoops.pmsg_size=0 (the diff between yours and mine is I set console_size to 0 and record_size to 2M, you do it the other way round). Dmesg is kept in "record_size". We don't need to preserve the console at all (unless there is something in console that isn't in dmesg but I've never seen that). > > > > > 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
