Re: [PATCH] kexec/powerpc: fix exporting memory limit

[Christophe Leroy]

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