Re: [Xen-devel] balloon question

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 9 Jun 2006, at 08:00, Jan Beulich wrote:

> > i386 deliberately marks pages beyond start_info->nr_pages as not
> > Reserved so they get picked up by the balloon driver. Either x86/64
> > needs to do the same, or we stop doing that in i386. But then there
> > will be pages that are legitimately Reserved that the balloon driver
> Where would, under Xen, such pages originate from? Namely beyond
> start_info->nr_pages?
>
> > will erroneously pick up. Or we could make the balloon driver
> > explicitly pick up all pages from start_info->nr_pages. Or have an
> It is already starting its scan at start_info->nr_pages.
I don't think there will currently be anything beyond ->nr_pages. So we 
could just get rid of the PageReserved test altogether.
But I think it's prefereable to take the following loop from 
i386/mm/init-xen.c and put it in x86/64's mem_init() somewhere:
 for (i = ...->nr_pages; i < max_pfn; i++) {
     ClearPageReserved(...);
     set_page_count(..., 1);
  }

That'll allow any architecture to reserve stuff beyond ->nr_pages 
without breaking the balloon driver. Could you try adding the above 
code and see how it works out?
 -- Keir


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