Invoke KVM_TDX_INIT in kvm_arch_pre_create_vcpu() that KVM_TDX_INIT
configures global TD configurations, e.g. the canonical CPUID config,
and must be executed prior to creating vCPUs.

Use kvm_x86_arch_cpuid() to setup the CPUID settings for TDX VM.

Note, this doesn't address the fact that QEMU may change the CPUID
configuration when creating vCPUs, i.e. punts on refactoring QEMU to
provide a stable CPUID config prior to kvm_arch_init().

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
---
Changes in v4:
- mark init_vm with g_autofree() and use QEMU_LOCK_GUARD() to eliminate
  the goto labels; (Daniel)
Changes in v3:
- Pass @errp in tdx_pre_create_vcpu() and pass error info to it. (Daniel)
---
 accel/kvm/kvm-all.c         |  9 +++++++-
 target/i386/kvm/kvm.c       |  9 ++++++++
 target/i386/kvm/meson.build |  2 +-
 target/i386/kvm/tdx-stub.c  |  8 ++++++++
 target/i386/kvm/tdx.c       | 41 +++++++++++++++++++++++++++++++++++++
 target/i386/kvm/tdx.h       |  4 ++++
 6 files changed, 71 insertions(+), 2 deletions(-)
 create mode 100644 target/i386/kvm/tdx-stub.c

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index a8a99d48e4ce..c9df41efa484 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -431,8 +431,15 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
 
     trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu));
 
+    /*
+     * tdx_pre_create_vcpu() may call cpu_x86_cpuid(). It in turn may call
+     * kvm_vm_ioctl(). Set cpu->kvm_state in advance to avoid NULL pointer
+     * dereference.
+     */
+    cpu->kvm_state = s;
     ret = kvm_arch_pre_create_vcpu(cpu, errp);
     if (ret < 0) {
+        cpu->kvm_state = NULL;
         goto err;
     }
 
@@ -440,11 +447,11 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
     if (ret < 0) {
         error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed (%lu)",
                          kvm_arch_vcpu_id(cpu));
+        cpu->kvm_state = NULL;
         goto err;
     }
 
     cpu->kvm_fd = ret;
-    cpu->kvm_state = s;
     cpu->vcpu_dirty = true;
     cpu->dirty_pages = 0;
     cpu->throttle_us_per_full = 0;
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 315998c8f7e5..1664ac49005e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -2271,6 +2271,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
     return r;
 }
 
+int kvm_arch_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+    if (is_tdx_vm()) {
+        return tdx_pre_create_vcpu(cpu, errp);
+    }
+
+    return 0;
+}
+
 int kvm_arch_destroy_vcpu(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
diff --git a/target/i386/kvm/meson.build b/target/i386/kvm/meson.build
index 26a1ab038513..460c5f8f85f3 100644
--- a/target/i386/kvm/meson.build
+++ b/target/i386/kvm/meson.build
@@ -7,7 +7,7 @@ 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_kvm_ss.add(when: 'CONFIG_TDX', if_true: files('tdx.c'), if_false: files('tdx-stub.c'))
 
 i386_system_ss.add(when: 'CONFIG_HYPERV', if_true: files('hyperv.c'), if_false: files('hyperv-stub.c'))
 
diff --git a/target/i386/kvm/tdx-stub.c b/target/i386/kvm/tdx-stub.c
new file mode 100644
index 000000000000..b614b46d3f4a
--- /dev/null
+++ b/target/i386/kvm/tdx-stub.c
@@ -0,0 +1,8 @@
+#include "qemu/osdep.h"
+
+#include "tdx.h"
+
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+    return -EINVAL;
+}
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 144acd8c9912..d548ec340285 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -475,6 +475,45 @@ static int tdx_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
     return 0;
 }
 
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
+{
+    MachineState *ms = MACHINE(qdev_get_machine());
+    X86CPU *x86cpu = X86_CPU(cpu);
+    CPUX86State *env = &x86cpu->env;
+    g_autofree struct kvm_tdx_init_vm *init_vm = NULL;
+    int r = 0;
+
+    QEMU_LOCK_GUARD(&tdx_guest->lock);
+    if (tdx_guest->initialized) {
+        return r;
+    }
+
+    init_vm = g_malloc0(sizeof(struct kvm_tdx_init_vm) +
+                        sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES);
+
+    r = kvm_vm_enable_cap(kvm_state, KVM_CAP_MAX_VCPUS, 0, ms->smp.cpus);
+    if (r < 0) {
+        error_setg(errp, "Unable to set MAX VCPUS to %d", ms->smp.cpus);
+        return r;
+    }
+
+    init_vm->cpuid.nent = kvm_x86_arch_cpuid(env, init_vm->cpuid.entries, 0);
+
+    init_vm->attributes = tdx_guest->attributes;
+
+    do {
+        r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, init_vm);
+    } while (r == -EAGAIN);
+    if (r < 0) {
+        error_setg_errno(errp, -r, "KVM_TDX_INIT_VM failed");
+        return r;
+    }
+
+    tdx_guest->initialized = true;
+
+    return 0;
+}
+
 /* tdx guest */
 OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
                                    tdx_guest,
@@ -487,6 +526,8 @@ static void tdx_guest_init(Object *obj)
 {
     TdxGuest *tdx = TDX_GUEST(obj);
 
+    qemu_mutex_init(&tdx->lock);
+
     tdx->attributes = 0;
 }
 
diff --git a/target/i386/kvm/tdx.h b/target/i386/kvm/tdx.h
index f62fe8ece982..0df910725b52 100644
--- a/target/i386/kvm/tdx.h
+++ b/target/i386/kvm/tdx.h
@@ -17,6 +17,9 @@ typedef struct TdxGuestClass {
 typedef struct TdxGuest {
     ConfidentialGuestSupport parent_obj;
 
+    QemuMutex lock;
+
+    bool initialized;
     uint64_t attributes;    /* TD attributes */
 } TdxGuest;
 
@@ -28,5 +31,6 @@ bool is_tdx_vm(void);
 
 void tdx_get_supported_cpuid(uint32_t function, uint32_t index, int reg,
                              uint32_t *ret);
+int tdx_pre_create_vcpu(CPUState *cpu, Error **errp);
 
 #endif /* QEMU_I386_TDX_H */
-- 
2.34.1