KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs

KVM: x86: #GP when attempts to write reserved bits of Variable Range MTRRs

Section 11.11.2.3 of the SDM mentions "All other bits in the IA32_MTRR_PHYSBASEn
and IA32_MTRR_PHYSMASKn registers are reserved; the processor generates a
general-protection exception(#GP) if software attempts to write to them". This
patch do it in kvm.

Signed-off-by: Wanpeng Li <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>