KVM: arm64: Handle guest stage-2 page-tables entirely at EL2

Now that EL2 is able to manage guest stage-2 page-tables, avoid
allocating a separate MMU structure in the host and instead introduce a
new fault handler which responds to guest stage-2 faults by sharing
GUP-pinned pages with the guest via a hypercall. These pages are
recovered (and unpinned) on guest teardown via the page reclaim
hypercall.

Signed-off-by: Will Deacon <will@kernel.org>
7 files changed