Continued the discussion on IRC: [10:19] <hws> cpaelzer: just to shortcut..... FWIW, this fix is only necessary if you have guest that use storage keys - e.g. an 16.04 guest should not trigger this problem. [10:21] <cpaelzer> hws: do we have any linux guests that use storgae keys in the meantime? [10:21] <cpaelzer> I might have lost track [10:21] <hws> cpaelzer: question for christian... [10:21] <cpaelzer> and as a HV host it is a bit weird, as you can only make "so much" assumption on your guests [10:22] <cpaelzer> who says no one uses a Ubuntu Xenial as host in 2020 (still supported then) with a new Guest that suddenly uses stroage keys [10:22] <cpaelzer> ... [10:22] <cpaelzer> anyway this is just the sort of discussion that I wanted on that bugzilla [10:22] <cpaelzer> for a more permanent documentation of the case [10:23] <cpaelzer> and since it is mirrored now this will happen [10:23] <cpaelzer> I don't mind loosing a few hours for the mirroring [10:32] <borntraeger> cpaelzer, hws no current Linux guest uses storage keys [10:32] <borntraeger> sles 11 and rhel6 do [10:32] <borntraeger> sles12, rhel7 ubuntu 16.04 do not [10:32] <cpaelzer> well the old one before we removed it [10:33] <cpaelzer> so since there is no intention to add storage keys back in Linux or host non Linux (not intention I'd know of) - the TL;DR is "not needed"? [10:40] <borntraeger> cpaelzer, unless you want to support some old debians as guest or so [10:45] <cpaelzer> borntraeger: did anybody check if there really is no perf impact? [10:45] <cpaelzer> I know that over time all pages will be used [10:45] <cpaelzer> but I thought the zero page would still be overloaded [10:45] <cpaelzer> or is even the fix [10:45] <cpaelzer> only active on storage key using guests [10:46] <cpaelzer> borntraeger: and so it is not only "not needed" but even when applied "not actively changing" the zero page handling as long as you have only "new" guests? [10:48] <borntraeger> cpaelzer, if a guest has a pattern of only reading a page, it will be a zero page inside the guest [10:49] <borntraeger> cpaelzer, the fix is to not use zero pages in the host to back guest pages
So leaving it to the kernel Team, but I'd think won't fix is correct for now. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1713765 Title: Consider "s390/mm: avoid empty zero pages for KVM guests to avoid postcopy hangs" for Artful To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1713765/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs