On 24.04.20 09:39, David Hildenbrand wrote: > On 23.04.20 18:29, Eric W. Biederman wrote: >> David Hildenbrand <david@xxxxxxxxxx> writes: >> >>>> The confusing part was talking about memory being still in use, >>>> that is actually scheduled for use in the future. >>> >>> +1 >>> >>>> >>>>>> Usually somewhere in the loaded image >>>>>> is a copy of the memory map at the time the kexec kernel was loaded. >>>>>> That will invalidate the memory map as well. >>>>> >>>>> Ah, unconditionally. Sure, x86 needs this. >>>>> (arm64 re-discovers the memory map from firmware tables after kexec) >>> >>> Does this include hotplugged DIMMs e.g., under KVM? >>> [...] >> >> As far as I know. If the memory map changes we need to drop the loaded >> image. >> >> >> Having thought about it a little more I suspect it would be the >> other way and just block all hotplug actions after a kexec_load. >> As all we expect to happen is running shutdown scripts. >> >> If blocking the hotplug action uses printk to print a nice message >> saying something like: "Hotplug blocked because of a loaded kexec image", >> then people will be able to figure out what is going on and >> call kexec -u if they haven't started the shutdown scripts yet. >> >> >> Either way it is something simple and unconditional that will make >> things work. >> > > Personally, I consider memory hotplug more important than keeping loaded > kexec data alive (just because somebody once decided to do a "kexec -l" > and never did a "kexec -e" we should not block any memory hot(un)plug - > especially in virtualized environments - for all eternity). > > So IMHO we would invalidate loaded kexec data (not the crashkernel, of > course) on memory hot(un)plug and print a warning. In addition, we can > let kexec-tools try to reload whatever they loaded after getting > notified that something changed. > > The "something changed" is visible to user space e.g., via udev events > for /sys/devices/memory/memoryX/ /sys/devices/system/memory/memoryX/ ... -- Thanks, David / dhildenb
