Re: [Patch 8/8] kexec: allow to shrink reserved memory

[Amerigo Wang]

KAMEZAWA Hiroyuki wrote:
> On Wed, 19 Aug 2009 10:41:13 +0800
> Amerigo Wang <amwang@xxxxxxxxxx> wrote:
>
>   
> > KAMEZAWA Hiroyuki wrote:
> >     
> > > On Tue, 18 Aug 2009 18:35:32 +0800
> > > Amerigo Wang <amwang@xxxxxxxxxx> wrote:
> > >
> > >   
> > >       
> > > > KAMEZAWA Hiroyuki wrote:
> > > >     
> > > >         
> > > > > On Tue, 18 Aug 2009 14:31:23 +0800
> > > > > Amerigo Wang <amwang@xxxxxxxxxx> wrote:
> > > > >   
> > > > >       
> > > > >           
> > > > > > >     It's hidden from the system before mem_init() ?
> > > > > > >   
> > > > > > >       
> > > > > > >           
> > > > > > >               
> > > > > > Not sure, but probably yes. It is reserved in setup_arch() which is 
> > > > > > before mm_init() which calls mem_init().
> > > > > >
> > > > > > Do you have any advice to free that reserved memory after boot? :)
> > > > > >
> > > > > >     
> > > > > >         
> > > > > >             
> > > > > Let's see arch/x86/mm/init.c::free_initmem()
> > > > >
> > > > > Maybe it's all you want.
> > > > >
> > > > > 	- ClearPageReserved()
> > > > > 	- init_page_count()
> > > > > 	- free_page()
> > > > > 	- totalram_pages++
> > > > >   
> > > > >       
> > > > >           
> > > > Just FYI: calling ClearPageReserved() caused an oops: "Unable to handle 
> > > > paging request".
> > > >
> > > > I am trying to figure out why...
> > > >
> > > >     
> > > >         
> > > Hmm...then....memmap is not there.
> > > pfn_valid() check will help you. What arch ? x86-64 ?
> > >   
> > >       
> > Hmm, yes, x86_64, but this code is arch-independent, I mean it should 
> > work or not work on all arch, no?
> >
> > So I am afraid we need to use other API to free it...
> >
> >     
> The, problem is whether memmap is there or not. That's all.
> plz see init sequence and check there are memmap.
> If memory-for-crash is obtained via bootmem,
> Don't you try to free memory hole ?
>   

Hi,

It looks like that mem_map has 'struct page' for the reserved memory, I 
checked my "early_node_map[] active PFN ranges" output, the reserved 
memory area for crash kernel is right in one range. Am I missing 
something here?

I don't know why that oops comes out, maybe because of no PTE for thoese 
pages?

Thanks.


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