KVM: x86: do not reset mmu if CR0.CD and CR0.NW are changed

CR0.CD and CR0.NW are not used by shadow page table so that need
not adjust mmu if these two bit are changed

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -572,8 +572,7 @@ out:
 int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
 	unsigned long old_cr0 = kvm_read_cr0(vcpu);
-	unsigned long update_bits = X86_CR0_PG | X86_CR0_WP |
-				    X86_CR0_CD | X86_CR0_NW;
+	unsigned long update_bits = X86_CR0_PG | X86_CR0_WP;
 
 	cr0 |= X86_CR0_ET;