i386/tdx: Disable PIC for TDX VMs

Legacy PIC (8259) cannot be supported for TDX VMs since TDX module
doesn't allow directly interrupt injection.  Using posted interrupts
for the PIC is not a viable option as the guest BIOS/kernel will not
do EOI for PIC IRQs, i.e. will leave the vIRR bit set.

Hence disable PIC for TDX VMs and error out if user wants PIC.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-38-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 87c5bf04960f1996700f6ecf1629088bbbf1081a..32c3f3795d04b615e19e19c172b77004f8c52942 100644 (file)
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -381,6 +381,13 @@ static int tdx_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
         return -EINVAL;
     }
 
+    if (x86ms->pic == ON_OFF_AUTO_AUTO) {
+        x86ms->pic = ON_OFF_AUTO_OFF;
+    } else if (x86ms->pic == ON_OFF_AUTO_ON) {
+        error_setg(errp, "TDX VM doesn't support PIC");
+        return -EINVAL;
+    }
+
     if (!tdx_caps) {
         r = get_tdx_capabilities(errp);
         if (r) {