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

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

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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