Hi guys, On 22/04/2020 17:40, David Hildenbrand wrote: >>>> 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? If you advertise hotplugged memory to the guest using ACPI, yes. We don't have a practical mechanism to pass 'fact's about the platform between kernels, instead we rely on those facts being discoverable, or described by firmware. >>>> All of this should be for a very brief window of a few seconds, as >>>> the loaded kexec image is quite short. >>> >>> It seems I'm the outlier anticipating anything could happen between >>> those syscalls. >> >> The design is: >> sys_kexec_load() >> shutdown scripts >> sys_reboot(LINUX_REBOOT_CMD_KEXEC); >> >> There are two system call simply so that the shutdown scripts can run. >> Now maybe someone somewhere does something different but that is not >> expected. [...] > Yes, and AFAIK, memory blocks which hold the reserved crashkernel area > can usually not get offlined and, therefore, the memory cannot get removed. The crashkernel area on arm64 will always land in un-removable memory. We set PG_Reserved on it too. Thanks, James
