> On Thu, 2014-03-06 at 18:24 +0400, Nikita Yushchenko wrote: > > When preparing dump-capturing kernel, kexec userspace tool needs to > > know actual amount of memory used by the running kernel. This may > > differ from extire available DRAM for a couple of reasons. To address > > this issue, kdump kernel support code injects several attributes into > > device tree that are later captured by userspace kexec tool via /proc > > interface. > > > > One such attrubute is 'chosen/linux,memory_limit' that is used to pass > > memory limit of the running kernel. > > > > This was initialized using kernel's 'memory_limit' variable, that is > > set by early init code based on mem= kernel parameter and other > > reasons. > > > > But there are cases when memory_limit variable does not contain proper > > information. One such case is when !CONFIG_HIGHMEM kernel runs on > > system with memory large enough not to fit into lowmem. > > Why doesn't the !CONFIG_HIGHMEM code update memory_limit to reflect > reality. I guess because memory_limit is used for ... well, memory limit, set by mem=. And for the rest memblock is used (and it *is* updated). And code elsewhere does use memblock, see e.g. numa_enforce_memory_limit() in arch/powerpc/mm/numa.c In MMU init (MMU_init() in arch/powerpc/mm/init_32.c -which is the point where final memory configuration is set) memblock, not memory_limit, is both used and updated.
