Which architectures need to sync vmalloc mappings between processes?

[Jeremy Fitzhardinge <jeremy@goop.org>]

Hi,

I'm looking at making all architectures export a vmalloc_sync_all()
function, so that generic code can be sure that a particular vmalloc
mapping is present in all address spaces.   I need this to implement a
function to reserve a chunk of vmalloc address space complete with
constructed pagetables, but without allocating any actual data pages.

On i386 with PAE, this is not necessary because the kernel's mappings
are shared between all processes anyway, so it would be a no-op.  
However, non-PAE i386 has a separate kernel mapping for each process,
and so needs to sync them - typically lazily on faults, but
vmalloc_sync_all exists to allow mass syncing when required.

What other architectures would require syncing of vmalloc mappings, and
what architectures would implement it as a no-op?

Thanks,
    J
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