i386: Introduce tdx-guest object

Introduce tdx-guest object which inherits X86_CONFIDENTIAL_GUEST,
and will be used to create TDX VMs (TDs) by

  qemu -machine ...,confidential-guest-support=tdx0	\
       -object tdx-guest,id=tdx0

It has one QAPI member 'attributes' defined, which allows user to set
TD's attributes directly.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-3-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configs/devices/i386-softmmu/default.mak

@@ -18,6 +18,7 @@
 #CONFIG_QXL=n
 #CONFIG_SEV=n
 #CONFIG_SGA=n
+#CONFIG_TDX=n
 #CONFIG_TEST_DEVICES=n
 #CONFIG_TPM_CRB=n
 #CONFIG_TPM_TIS_ISA=n

hw/i386/Kconfig

@@ -10,6 +10,10 @@ config SGX
     bool
     depends on KVM
 
+config TDX
+    bool
+    depends on KVM
+
 config PC
     bool
     imply APPLESMC
@@ -26,6 +30,7 @@ config PC
     imply QXL
     imply SEV
     imply SGX
+    imply TDX
     imply TEST_DEVICES
     imply TPM_CRB
     imply TPM_TIS_ISA

qapi/qom.json

@@ -1047,6 +1047,19 @@
             '*host-data': 'str',
             '*vcek-disabled': 'bool' } }
 
+##
+# @TdxGuestProperties:
+#
+# Properties for tdx-guest objects.
+#
+# @attributes: The 'attributes' of a TD guest that is passed to
+#     KVM_TDX_INIT_VM
+#
+# Since: 10.1
+##
+{ 'struct': 'TdxGuestProperties',
+  'data': { '*attributes': 'uint64' } }
+
 ##
 # @ThreadContextProperties:
 #
@@ -1132,6 +1145,7 @@
     'sev-snp-guest',
     'thread-context',
     's390-pv-guest',
+    'tdx-guest',
     'throttle-group',
     'tls-creds-anon',
     'tls-creds-psk',
@@ -1204,6 +1218,7 @@
                                       'if': 'CONFIG_SECRET_KEYRING' },
       'sev-guest':                  'SevGuestProperties',
       'sev-snp-guest':              'SevSnpGuestProperties',
+      'tdx-guest':                  'TdxGuestProperties',
       'thread-context':             'ThreadContextProperties',
       'throttle-group':             'ThrottleGroupProperties',
       'tls-creds-anon':             'TlsCredsAnonProperties',

target/i386/kvm/meson.build

@@ -8,6 +8,8 @@ i386_kvm_ss.add(files(
 
 i386_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files('xen-emu.c'))
 
+i386_kvm_ss.add(when: 'CONFIG_TDX', if_true: files('tdx.c'))
+
 i386_system_ss.add(when: 'CONFIG_HYPERV', if_true: files('hyperv.c'), if_false: files('hyperv-stub.c'))
 
 i386_system_ss.add_all(when: 'CONFIG_KVM', if_true: i386_kvm_ss)

target/i386/kvm/tdx.c

@@ -0,0 +1,43 @@
+/*
+ * QEMU TDX support
+ *
+ * Copyright (c) 2025 Intel Corporation
+ *
+ * Author:
+ *      Xiaoyao Li <xiaoyao.li@intel.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "qom/object_interfaces.h"
+
+#include "tdx.h"
+
+/* tdx guest */
+OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
+                                   tdx_guest,
+                                   TDX_GUEST,
+                                   X86_CONFIDENTIAL_GUEST,
+                                   { TYPE_USER_CREATABLE },
+                                   { NULL })
+
+static void tdx_guest_init(Object *obj)
+{
+    ConfidentialGuestSupport *cgs = CONFIDENTIAL_GUEST_SUPPORT(obj);
+    TdxGuest *tdx = TDX_GUEST(obj);
+
+    cgs->require_guest_memfd = true;
+    tdx->attributes = 0;
+
+    object_property_add_uint64_ptr(obj, "attributes", &tdx->attributes,
+                                   OBJ_PROP_FLAG_READWRITE);
+}
+
+static void tdx_guest_finalize(Object *obj)
+{
+}
+
+static void tdx_guest_class_init(ObjectClass *oc, const void *data)
+{
+}

target/i386/kvm/tdx.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef QEMU_I386_TDX_H
+#define QEMU_I386_TDX_H
+
+#include "confidential-guest.h"
+
+#define TYPE_TDX_GUEST "tdx-guest"
+#define TDX_GUEST(obj)  OBJECT_CHECK(TdxGuest, (obj), TYPE_TDX_GUEST)
+
+typedef struct TdxGuestClass {
+    X86ConfidentialGuestClass parent_class;
+} TdxGuestClass;
+
+typedef struct TdxGuest {
+    X86ConfidentialGuest parent_obj;
+
+    uint64_t attributes;    /* TD attributes */
+} TdxGuest;
+
+#endif /* QEMU_I386_TDX_H */