On Wed, Sep 13, 2023 at 06:03:12PM -0700, Stephen Brennan wrote: > Hello all, > > This is the second version of my patch series about the kdump format, > you can see the first version here [1]. > > The current output format for dump-guest-memory's kdump compressed > format is actually the "makedumpfile flattened" format. It was done > intentionally to allow the flexibility to write to non-seekable file > descriptors, like pipes [2], without using temporary files. Currently > libvirt uses this ability when VIR_DUMP_BYPASS_CACHE flag is set, to > avoid the dump process using page cache. The standard kdump output > format needs the page cache so that it can seek back and forth as part > of writing the dump file. > > So the default kdump dump format cannot be changed to the standard > format. This patch series adds the ability to use the standard format, > and adds a QMP / HMP argument to enable it. > > An open question for Daniel et al.: > > Would it be possible to make flattened the default only for libvirt? I > totally agree that this would be a bad backward incompatible change > there. But for QMP / HMP commands, I think using the standard, broadly > compatible format as the default is important for user friendliness. If > a user needs to know the difference between flavors of kdump formats > like the flattened format, in order to set the correct option, then > we've already lost.
The default is 'elf' - any use of kdump formats is already an opt-in, and with the new kdump variants represented as enums, the user can just specify which they want explicitly. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
