[PATCH v2 0/4] x86: shim building adjustments (plus shadow follow-on)

[Jan Beulich <jbeulich@xxxxxxxx>]

The first change is simply addressing a build issue noticed by
Andrew. The build breakage goes beyond this specific combination
though - PV_SHIM_EXCLUSIVE plus HVM is similarly an issue. This
is what the last patch tries to take care of, in a shape already
on irc noticed to be controversial. I'm submitting the change
nevertheless because for the moment there looks to be a majority
in favor of going this route. One argument not voiced there yet:
What good does it do to allow a user to enable HVM when then on
the resulting hypervisor they still can't run HVM guests (for
the hypervisor still being a dedicated PV shim one). On top of
this, the alternative approach is likely going to get ugly.

1: fix build with PV_SHIM_EXCLUSIVE and SHADOW_PAGING
2: adjust Kconfig defaults
3: don't permit HVM and PV_SHIM_EXCLUSIVE at the same time
4: refactor shadow_vram_{get,put}_l1e()

Jan