Re: [Xen-devel] [PATCH] x86-64 linux: unmap temporary mappings established for setup of 1:1 mappings

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 2 Jun 2006, at 08:29, Jan Beulich wrote:

> > I've applied this to -unstable, but in this patch I only see code to
> > destroy the extended init mappings. What happens if you have a really
> > big initrd (for example)? That will push the initial pagetables up 
> > into
> > the modules area -- is that handled correctly now or is more fixup
> > required?
> The initrd mappings, as I read it, get destroyed in setup_arch(). The 
> thing that also came to my mind were the
> Xen-created page tables, which might need taking care of. The main 
> issue here will be to precisely determine the
> boundary of where to start destruction - does Xen make any guarantees 
> regarding the ordering of things within the
> initial allocation?
Ah yes. Well, given that things like the console and xenbus pages are 
also above the initrd mapping, they must also be dealt with to properly 
be sure of a clear section of address space for modules.
I backed out the patch in -unstable since it didn't build. In any case 
I felt that it was doing more than just zapping the extra init mappings 
(it changed various bits and pieces, I think to allow safe calling of 
init_memory_mapping() after bootstrap, which I think we never currently 
do -- it belongs in a separate patch anyway).
I think I will wait until someone has a chance to look at this more 
thoroughly and can make a patch that zaps all the init mappings in one 
single place. I'll then look at backporting that patch to -testing.
 -- Keir


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