1. Please describe the problem: CONFIG_XEN_BALLOON_MEMORY_HOTPLUG is useful to allow dynamically increasing (Xen) VM beyond what was set in the memory map initially ("maxmem" vm.cfg setting), without rebooting it. Additionally, it allows faster VM startup when one is planning to give it more memory later: - with CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y: start VM with maxmem=memory (the initial "low" value) - no balloon driver is involved during boot; memory can be expanded later with `xl mem-max` and `xl mem-set` - without CONFIG_XEN_BALLOON_MEMORY_HOTPLUG: one need to start with sufficiently high maxmem (planning for future increases) and during the boot process the balloon driver gives back the difference to Xen - with init_on_free=1 (default nowadays) it also zeroes all those pages, which in some cases can add a few seconds to the VM start time (sometimes doubling it...). CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y is also necessary to increase memory beyond ~10x what was allocated at boot (without CONFIG_XEN_BALLOON_MEMORY_HOTPLUG higher "maxmem" parameter is not enough, as Linux doesn't reserve enough space at boot to account for more memory). 2. What is the Version-Release number of the kernel: 6.8.5-301.fc40.x86_64 (same applies to fc39) Reproducible: Always
A bit more context - I found it when using Qubes OS, which does highly dynamic memory management: https://github.com/QubesOS/qubes-issues/issues/7956#issuecomment-1533884519. But based on my testing, it applies to plain Xen too. Furthermore, starting a HVM with "maxmem">"memory" (maximum allocation > initial allocation) utilizes populate-on-demand functionality which had security issues in the past, for example: https://xenbits.xen.org/xsa/advisory-388.html
FEDORA-2024-1d25a668fe (kernel-6.8.7-200.fc39) has been submitted as an update to Fedora 39. https://bodhi.fedoraproject.org/updates/FEDORA-2024-1d25a668fe
FEDORA-2024-49fa41a18b (kernel-6.8.7-100.fc38) has been submitted as an update to Fedora 38. https://bodhi.fedoraproject.org/updates/FEDORA-2024-49fa41a18b
FEDORA-2024-d4cd1cc75f (kernel-6.8.7-300.fc40) has been submitted as an update to Fedora 40. https://bodhi.fedoraproject.org/updates/FEDORA-2024-d4cd1cc75f
FEDORA-2024-1d25a668fe has been pushed to the Fedora 39 testing repository. Soon you'll be able to install the update with the following command: `sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-1d25a668fe` You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-1d25a668fe See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.
FEDORA-2024-d4cd1cc75f has been pushed to the Fedora 40 testing repository. Soon you'll be able to install the update with the following command: `sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-d4cd1cc75f` You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-d4cd1cc75f See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.
FEDORA-2024-49fa41a18b has been pushed to the Fedora 38 testing repository. Soon you'll be able to install the update with the following command: `sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-49fa41a18b` You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-49fa41a18b See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.
FEDORA-2024-d4cd1cc75f (kernel-6.8.7-300.fc40) has been pushed to the Fedora 40 stable repository. If problem still persists, please make note of it in this bug report.
FEDORA-2024-1d25a668fe (kernel-6.8.7-200.fc39) has been pushed to the Fedora 39 stable repository. If problem still persists, please make note of it in this bug report.
FEDORA-2024-49fa41a18b (kernel-6.8.7-100.fc38) has been pushed to the Fedora 38 stable repository. If problem still persists, please make note of it in this bug report.