KVM: x86: emulate #UD while in guest mode

KVM: x86: emulate #UD while in guest mode

This reverts commits 07a2755835a7a8b2b08549a63eb64f7f3ea4c870
and 4445222010839ab74af07819c9618bd2fb13627c.

If the hardware doesn't support MOVBE, but L0 sets CPUID.01H:ECX.MOVBE
in L1's emulated CPUID information, then L1 is likely to pass that
CPUID bit through to L2. L2 will expect MOVBE to work, but if L1
doesn't intercept #UD, then any MOVBE instruction executed in L2 will
raise #UD, and the exception will be delivered in L2.

Commit 4445222010839ab74af07819c9618bd2fb13627c is a better and more
complete version of 07a2755835a7 ("KVM: nVMX: Do not emulate #UD while
in guest mode"); however, neither considers the above case.

Suggested-by: Jim Mattson <jmattson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>