>+static int tdx_emulate_io(struct kvm_vcpu *vcpu)
>+{
>+ struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
>+ unsigned long val = 0;
>+ unsigned int port;
>+ int size, ret;
>+ bool write;
..
>+
>+ ++vcpu->stat.io_exits;
>+
>+ size = tdvmcall_a0_read(vcpu);
>+ write = tdvmcall_a1_read(vcpu);
a1 (i.e., R13) should be either 0 or 1. Other values are reserved according to
the GHCI spec. It is not appropriate to cast it to a boolean. For example, if
R13=2, KVM shouldn't treat it as a write request; instead, this request should
be rejected.
>+ port = tdvmcall_a2_read(vcpu);
>+
>+ if (size != 1 && size != 2 && size != 4) {
>+ tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND);
>+ return 1;
>+ }
