TDX doesn't support SMM and VMM cannot emulate SMM for TDX VMs because
VMM cannot manipulate TDX VM's memory.

Disable SMM for TDX VMs and error out if user requests to enable SMM.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
---
 target/i386/kvm/tdx.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 4fbb18135951..7eb3628763ae 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -695,11 +695,19 @@ static Notifier tdx_machine_done_notify = {
 
 int tdx_kvm_init(MachineState *ms, Error **errp)
 {
+    X86MachineState *x86ms = X86_MACHINE(ms);
     TdxGuest *tdx = TDX_GUEST(OBJECT(ms->cgs));
     int r = 0;
 
     ms->require_guest_memfd = true;
 
+    if (x86ms->smm == ON_OFF_AUTO_AUTO) {
+        x86ms->smm = ON_OFF_AUTO_OFF;
+    } else if (x86ms->smm == ON_OFF_AUTO_ON) {
+        error_setg(errp, "TDX VM doesn't support SMM");
+        return -EINVAL;
+    }
+
     if (!tdx_caps) {
         r = get_tdx_capabilities(errp);
         if (r) {
-- 
2.34.1