Add TDX Guest detection

README.md

@@ -435,6 +435,7 @@ Exit Code 1
 | SYSCALL            | System-Call Extension (SCE): SYSCALL and SYSRET instructions.                                                                                                                      |
 | SYSEE              | SYSENTER and SYSEXIT instructions                                                                                                                                                  |
 | TBM                | AMD Trailing Bit Manipulation                                                                                                                                                      |
+| TDX_GUEST          | Intel Trust Domain Extensions Guest                                                                                                                                                |
 | TLB_FLUSH_NESTED   | AMD: Flushing includes all the nested translations for guest translations                                                                                                          |
 | TME                | Intel Total Memory Encryption. The following MSRs are supported: IA32_TME_CAPABILITY, IA32_TME_ACTIVATE, IA32_TME_EXCLUDE_MASK, and IA32_TME_EXCLUDE_BASE.                         |
 | TOPEXT             | TopologyExtensions: topology extensions support. Indicates support for CPUID Fn8000_001D_EAX_x[N:0]-CPUID Fn8000_001E_EDX.                                                         |

cpuid.go

@@ -226,6 +226,7 @@ const (
 	SYSCALL                             // System-Call Extension (SCE): SYSCALL and SYSRET instructions.
 	SYSEE                               // SYSENTER and SYSEXIT instructions
 	TBM                                 // AMD Trailing Bit Manipulation
+	TDX_GUEST                           // Intel Trust Domain Extensions Guest
 	TLB_FLUSH_NESTED                    // AMD: Flushing includes all the nested translations for guest translations
 	TME                                 // Intel Total Memory Encryption. The following MSRs are supported: IA32_TME_CAPABILITY, IA32_TME_ACTIVATE, IA32_TME_EXCLUDE_MASK, and IA32_TME_EXCLUDE_BASE.
 	TOPEXT                              // TopologyExtensions: topology extensions support. Indicates support for CPUID Fn8000_001D_EAX_x[N:0]-CPUID Fn8000_001E_EDX.
@@ -1393,6 +1394,13 @@ func support() flagSet {
 		fs.setIf((a>>24)&1 == 1, VMSA_REGPROT)
 	}
 
+	if mfi >= 0x21 {
+		// Intel Trusted Domain Extensions Guests have their own cpuid leaf (0x21).
+		_, ebx, ecx, edx := cpuid(0x21)
+		identity := string(valAsString(ebx, edx, ecx))
+		fs.setIf(identity == "IntelTDX    ", TDX_GUEST)
+	}
+
 	return fs
 }