KVM: nVMX: Validate the IA32_BNDCFGS on nested VM-entry

According to the SDM, if the "load IA32_BNDCFGS" VM-entry controls is 1, the
following checks are performed on the field for the IA32_BNDCFGS MSR:
 - Bits reserved in the IA32_BNDCFGS MSR must be 0.
 - The linear address in bits 63:12 must be canonical.
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx.c

@@ -10876,6 +10876,11 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 			return 1;
 	}
 
+	if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS) &&
+		(is_noncanonical_address(vmcs12->guest_bndcfgs & PAGE_MASK, vcpu) ||
+		(vmcs12->guest_bndcfgs & MSR_IA32_BNDCFGS_RSVD)))
+			return 1;
+
 	return 0;
 }