On 13.06.22 10:53, Florian M?ller wrote: >>>>>>>> >>>>>>>> Issues showed up when I set up a Kali Linux Guest. I missed >>>>>>>> the memory configuration before booting up the instance, so >>>>>>>> it started with 1GB of memory, and ballooning active between >>>>>>>> 512MB and several TB of memory. Hyper-V started to allocate >>>>>>>> more and more memory to this guest since the reported memory >>>>>>>> requirements also increased. The guest kernel didn't see any >>>>>>>> of that allocated memory, as far as I can tell. > > Please do not forget about this: (emoji-pointing-up) > >>>>> >>>>> Yes, that looks like a good solution. I didn't remember that there >>>>> is a kernel config option to automatically do the onlining. With >>>>> this kernel option enabled, using a udev rule obviously isn't >>>>> needed. The kernel option was added in Linux kernel version 4.7, >>>>> which might be after the last time I looked at Hyper-V memory hot-add >> in detail. >>>>> >>>>> Michael >>>>> >>>> >>>> Awesome! >>>> >>>> Last question: Since not having the kernel option by default and also >>>> not having the udev rule in some distributions causes the Hyper-V >>>> host to eat up all the memory up to the defined limit (and to die >>>> eventually), should this be considered as a bug? And if the answer is >>>> no, how can I (or anyone) forward the requirement to the publishers to >> be solved at the source? >>>> >>>> Thank you! >>>> >>> >>> It's unclear whether this should be treated as a bug. We certainly >>> want the "right" thing to happen as seamlessly as possible, but there >>> are tradeoffs. Back when Vitaly Kuznetsov added >>> CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE, >>> I can see there was some debate about whether this option should be >>> enabled by default. There was reluctance to do so because of potential >>> backwards compatibility problems with other environments. When >>> hot-adding real physical memory to a bare-metal server, apparently you >>> don't want to automatically online the added memory. > > By bug I meant the effects on the hypervisor (see above). A guest without proper onlining of newly added memory is currently able to choke the host to standstill. That's a hypervisor bug. -- Thanks, David / dhildenb
