Jeremy Fitzhardinge wrote:
PAE mode requires that we reload cr3 in order to guarantee that
changes to the pgd will be noticed by the processor. This means that
in principle pud_clear needs to reload cr3 every time. However,
because reloading cr3 implies a tlb flush, we want to avoid it where
possible.
It only matters (for a processor which supports PGE) if we actually use
the namespace in between.
In huge_pmd_unshare, it is followed by flush_tlb_range, which always
results in a full cr3-reload tlb flush.
This one makes me nervous, as it feels like a side effect of
implementation, and not a guarantee by design.
-hpa
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