x86/CPUID: block speculative out-of-bound accesses

x86/CPUID: block speculative out-of-bound accesses

During instruction emulation, the cpuid instruction is emulated with
data that is controlled by the guest. As speculation might pass bound
checks, we have to ensure that no out-of-bound loads are possible.

To not rely on the compiler to perform value propagation, instead of
using the array_index_nospec macro, we replace the variable with the
constant to be propagated instead.

This commit is part of the SpectreV1+L1TF mitigation patch series.

Signed-off-by: Norbert Manthey <nmanthey@amazon.de>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>