ARM ARM926EJ-S Technical Reference Manual page 84

Memory Management Unit
3-20
Note
The domain specified in the first-level description and access permissions specified in
the first-level description together determine whether the access has permissions to
proceed. See section Domain access control on page 3-24 for details.
Subpages
You can define access permissions for subpages of small and large pages. If, during a
page table walk, a small or large page has a different subpage permission, only the
subpage being accessed is written into the TLB. For example, a 16KB (large page)
subpage entry is written into the TLB if the subpage permission differs, and a 64KB
entry is put in the TLB if the subpage permissions are identical.
When you use subpage permissions, and the page entry then has to be invalidated, you
must invalidate all four subpages separately.
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