* Thomas Huth (th...@redhat.com) wrote: > That would mean a regression compared to what we have today. Currently, > the ballooning is working OK for 64k guests on a 64k ppc host - rather > by chance than on purpose, but it's working. The guest is always sending > all the 4k fragments of a 64k page, and QEMU is trying to call madvise() > for every one of them, but the kernel is ignoring madvise() on > non-64k-aligned addresses, so we end up with a situation where the > madvise() frees a whole 64k page which is also declared as free by the > guest.
I wouldn't worry about migrating your fragmenet map; but I wonder if it needs to be that complex - does the guest normally do something more sane like do the 4k pages in order and so you've just got to track the last page it tried rather than having a full map? A side question is whether the behaviour that's seen by virtio_ballon_handle_output is always actually the full 64k page; it calls balloon_page once for each message/element - but if all of those elements add back up to the full page, perhaps it makes more sense to reassemble it there? > I think we should either take this patch as it is right now (without > adding extra code for migration) and later update it to the bitmap code > by Jitendra Kolhe, or omit it completely (leaving 4k guests broken) and > fix it properly after the bitmap code has been applied. But disabling > the balloon code for 64k guests on 64k hosts completely does not sound > very appealing to me. What do you think? Yeh I agree; your existing code should work and I don't think we should break 64k-on-64k. Dave > > Thomas > -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
