tree 630dbc2032df606566f7249aa326c1e2a120c1ce
parent 15ce60056b24a65b65e28de973a9fd8ac0750a2f
author Jeremy Fitzhardinge <jeremy@goop.org> 1212193467 +0100
committer Ingo Molnar <mingo@elte.hu> 1212405880 +0200

xen: avoid hypercalls when updating unpinned pud/pmd

When operating on an unpinned pagetable (ie, one under construction or
destruction), it isn't necessary to use a hypercall to update a
pud/pmd entry.  Jan Beulich observed that a similar optimisation
avoided many thousands of hypercalls while doing a kernel build.

One tricky part is that early in the kernel boot there's no page
structure, so we can't check to see if the page is pinned.  In that
case, we just always use the hypercall.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>