TDX VM requires VM type KVM_X86_TDX_VM to be passed to
kvm_ioctl(KVM_CREATE_VM). Hence implement mc->kvm_type() for i386
architecture.

If tdx-guest object is specified to confidential-guest-support, like,

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

it parses VM type as KVM_X86_TDX_VM. Otherwise, it's KVM_X86_DEFAULT_VM.

Also store the vm_type in MachineState for other code to query what the
VM type is.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
---
Changes in v4:
 - fix the build error of kvm_get_vm_type() when --disable-kvm;
---
 hw/i386/x86.c              | 12 ++++++++++++
 include/hw/i386/x86.h      |  1 +
 target/i386/kvm/kvm.c      | 30 ++++++++++++++++++++++++++++++
 target/i386/kvm/kvm_i386.h |  1 +
 4 files changed, 44 insertions(+)

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 2b6291ad8d5f..f66a92f6c9cc 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -1386,6 +1386,17 @@ static void machine_set_sgx_epc(Object *obj, Visitor *v, const char *name,
     qapi_free_SgxEPCList(list);
 }
 
+static int x86_kvm_type(MachineState *ms, const char *vm_type)
+{
+    X86MachineState *x86ms = X86_MACHINE(ms);
+    int kvm_type;
+
+    kvm_type = kvm_enabled() ? kvm_get_vm_type(ms, vm_type) : 0;
+    x86ms->vm_type = kvm_type;
+
+    return kvm_type;
+}
+
 static void x86_machine_initfn(Object *obj)
 {
     X86MachineState *x86ms = X86_MACHINE(obj);
@@ -1410,6 +1421,7 @@ static void x86_machine_class_init(ObjectClass *oc, void *data)
     mc->cpu_index_to_instance_props = x86_cpu_index_to_props;
     mc->get_default_cpu_node_id = x86_get_default_cpu_node_id;
     mc->possible_cpu_arch_ids = x86_possible_cpu_arch_ids;
+    mc->kvm_type = x86_kvm_type;
     x86mc->save_tsc_khz = true;
     x86mc->fwcfg_dma_enabled = true;
     nc->nmi_monitor_handler = x86_nmi;
diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h
index da19ae15463a..ab1d38569019 100644
--- a/include/hw/i386/x86.h
+++ b/include/hw/i386/x86.h
@@ -41,6 +41,7 @@ struct X86MachineState {
     MachineState parent;
 
     /*< public >*/
+    unsigned int vm_type;
 
     /* Pointers to devices and objects: */
     ISADevice *rtc;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 42970ab046fa..c961846777cc 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -32,6 +32,7 @@
 #include "sysemu/runstate.h"
 #include "kvm_i386.h"
 #include "sev.h"
+#include "tdx.h"
 #include "xen-emu.h"
 #include "hyperv.h"
 #include "hyperv-proto.h"
@@ -161,6 +162,35 @@ static KVMMSRHandlers msr_handlers[KVM_MSR_FILTER_MAX_RANGES];
 static RateLimit bus_lock_ratelimit_ctrl;
 static int kvm_get_one_msr(X86CPU *cpu, int index, uint64_t *value);
 
+static const char *vm_type_name[] = {
+    [KVM_X86_DEFAULT_VM] = "default",
+    [KVM_X86_TDX_VM] = "tdx",
+};
+
+int kvm_get_vm_type(MachineState *ms, const char *vm_type)
+{
+    int kvm_type = KVM_X86_DEFAULT_VM;
+
+    if (ms->cgs && object_dynamic_cast(OBJECT(ms->cgs), TYPE_TDX_GUEST)) {
+        kvm_type = KVM_X86_TDX_VM;
+    }
+
+    /*
+     * old KVM doesn't support KVM_CAP_VM_TYPES and KVM_X86_DEFAULT_VM
+     * is always supported
+     */
+    if (kvm_type == KVM_X86_DEFAULT_VM) {
+        return kvm_type;
+    }
+
+    if (!(kvm_check_extension(KVM_STATE(ms->accelerator), KVM_CAP_VM_TYPES) & BIT(kvm_type))) {
+        error_report("vm-type %s not supported by KVM", vm_type_name[kvm_type]);
+        exit(1);
+    }
+
+    return kvm_type;
+}
+
 bool kvm_has_smm(void)
 {
     return kvm_vm_check_extension(kvm_state, KVM_CAP_X86_SMM);
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 30fedcffea3e..55fb25fa8e2e 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -37,6 +37,7 @@ bool kvm_hv_vpindex_settable(void);
 bool kvm_enable_sgx_provisioning(KVMState *s);
 bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);
 
+int kvm_get_vm_type(MachineState *ms, const char *vm_type);
 void kvm_arch_reset_vcpu(X86CPU *cs);
 void kvm_arch_after_reset_vcpu(X86CPU *cpu);
 void kvm_arch_do_init_vcpu(X86CPU *cs);
-- 
2.34.1