Quick note on focal: $ rmadison --arch=s390x linux-generic | grep focal linux-generic | 5.3.0.18.21 | focal | s390x linux-generic | 5.3.0.21.24 | focal-proposed | s390x
$ grep CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE /boot/config-5.3.0-21-generic # CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE is not set $ grep CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE /boot/config-5.3.0-18-generic CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y (so it's currently in proposed) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1848492 Title: Change Config Option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE for s390x from yes to no Status in Ubuntu on IBM z Systems: Fix Committed Status in linux package in Ubuntu: Fix Committed Status in linux source package in Bionic: Fix Released Status in linux source package in Disco: Fix Released Status in linux source package in Eoan: Fix Released Bug description: SRU Justification: ================== [Impact] * By default all standby memory that is configured to an LPAR is used at boot (IPL) time. * But the standby memory is meant to be added and used on demand later (after IPL). [Fix] * 0001-Ubuntu-Config-Disabled-CONFIG_MEMORY_HOTPLUG_DEFAULT.patch [Test Case] * Configure an LPAR in it's Activation Profile with a certain amount of 'Initial' memory and some 'Reserved' memory on top. * Re-activate the LPAR to make the changes take effect and boot (IPL) Ubuntu. * Check with the help of free whether the reported memory is only the initial memory (actual) or initial+reserved (desired). [Regression Potential] * There is a certain regression potential, since some systems may have Initial and Reserved memory already defined today and have it already all in use under Linux (today obviously w/o having it dynamically added). * If such a system got re-activated and rebooted, the memory size will then be what's defined as Initial memory and no longer Initial+Reserved. * To be able to use the same size of the memory than before, the Reserved memory need to be either dynamically be added or the Initial memory re-configured to the sum of former Initial+Reserved. * The latter case requires a re-activation of the LPAR, but since this corner case only happens after a reboot, a downtime is already in place for the re-activation. * But overall the regression potential is low since it's for s390x only and the 'Reserved' memory option in the Activation Profile is rarely used. [Other Info] * In the past this config option was diabled for ppc64el, too. __________ The Ubuntu kernel configuration contains CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y for s390. This causes all standby memory configured for an LPAR to be used at IPL time. Note that this is definetaly not what a user wants on s390. The normal process is: define a certain amount of "base" memory which the system should use when IPL'ed, and define also a certain amount of "standby" memory which can be (also only partially) be additionaly used when necessary. Also note that it is *not* possible to add additional memory to a runnung system, besides the amount of memory specified as "standby". Therefore please change the kernel config option CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE to "n" for s390. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1848492/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
