KVM: arm64: Reacquire exclusive pin when unsharing a page

When a page is unshared by a protected guest, ensure that it is
not possible to obtain further pins on it, to avoid the issues
mentioned earlier.

Note that this will fail if there is more than one regular pin on
the page, and the guest is notified.

Signed-off-by: Fuad Tabba <tabba@google.com>
3 files changed