Le 07/03/2014 à 05:38, Nikita Yushchenko a écrit :
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.
We still have this patch as "New" in patchwork.
I don't know if it is relevant but directory structure has changed so if
still needed this patch needs rebase.
Christophe
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