KVM provides TDX capabilities via sub command KVM_TDX_CAPABILITIES of
IOCTL(KVM_MEMORY_ENCRYPT_OP). Get the capabilities when initializing
TDX context. It will be used to validate user's setting later.

Since there is no interface reporting how many cpuid configs contains in
KVM_TDX_CAPABILITIES, QEMU chooses to try starting with a known number
and abort when it exceeds KVM_MAX_CPUID_ENTRIES.

Besides, introduce the interfaces to invoke TDX "ioctls" at different
scope (KVM, VM and VCPU) in preparation.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
---
Changes in v4:
- use {} to initialize struct kvm_tdx_cmd, to avoid memset();
- remove tdx_platform_ioctl() because no user;

Changes in v3:
- rename __tdx_ioctl() to tdx_ioctl_internal()
- Pass errp in get_tdx_capabilities();

changes in v2:
  - Make the error message more clear;

changes in v1:
  - start from nr_cpuid_configs = 6 for the loop;
  - stop the loop when nr_cpuid_configs exceeds KVM_MAX_CPUID_ENTRIES;
---
 target/i386/kvm/kvm.c      |  2 -
 target/i386/kvm/kvm_i386.h |  2 +
 target/i386/kvm/tdx.c      | 91 +++++++++++++++++++++++++++++++++++++-
 3 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 3f1d2272fb06..ddbcd1071a7e 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1686,8 +1686,6 @@ static int hyperv_init_vcpu(X86CPU *cpu)
 
 static Error *invtsc_mig_blocker;
 
-#define KVM_MAX_CPUID_ENTRIES  100
-
 static void kvm_init_xsave(CPUX86State *env)
 {
     if (has_xsave2) {
diff --git a/target/i386/kvm/kvm_i386.h b/target/i386/kvm/kvm_i386.h
index 55fb25fa8e2e..c3ef46a97a7b 100644
--- a/target/i386/kvm/kvm_i386.h
+++ b/target/i386/kvm/kvm_i386.h
@@ -13,6 +13,8 @@
 
 #include "sysemu/kvm.h"
 
+#define KVM_MAX_CPUID_ENTRIES  100
+
 #ifdef CONFIG_KVM
 
 #define kvm_pit_in_kernel() \
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 621a05beeb4e..ad76abd58373 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -12,17 +12,106 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "qom/object_interfaces.h"
+#include "sysemu/kvm.h"
 
 #include "hw/i386/x86.h"
+#include "kvm_i386.h"
 #include "tdx.h"
 
+static struct kvm_tdx_capabilities *tdx_caps;
+
+enum tdx_ioctl_level{
+    TDX_VM_IOCTL,
+    TDX_VCPU_IOCTL,
+};
+
+static int tdx_ioctl_internal(void *state, enum tdx_ioctl_level level, int cmd_id,
+                        __u32 flags, void *data)
+{
+    struct kvm_tdx_cmd tdx_cmd = {};
+    int r;
+
+    tdx_cmd.id = cmd_id;
+    tdx_cmd.flags = flags;
+    tdx_cmd.data = (__u64)(unsigned long)data;
+
+    switch (level) {
+    case TDX_VM_IOCTL:
+        r = kvm_vm_ioctl(kvm_state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
+        break;
+    case TDX_VCPU_IOCTL:
+        r = kvm_vcpu_ioctl(state, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
+        break;
+    default:
+        error_report("Invalid tdx_ioctl_level %d", level);
+        exit(1);
+    }
+
+    return r;
+}
+
+static inline int tdx_vm_ioctl(int cmd_id, __u32 flags, void *data)
+{
+    return tdx_ioctl_internal(NULL, TDX_VM_IOCTL, cmd_id, flags, data);
+}
+
+static inline int tdx_vcpu_ioctl(void *vcpu_fd, int cmd_id, __u32 flags,
+                                 void *data)
+{
+    return  tdx_ioctl_internal(vcpu_fd, TDX_VCPU_IOCTL, cmd_id, flags, data);
+}
+
+static int get_tdx_capabilities(Error **errp)
+{
+    struct kvm_tdx_capabilities *caps;
+    /* 1st generation of TDX reports 6 cpuid configs */
+    int nr_cpuid_configs = 6;
+    size_t size;
+    int r;
+
+    do {
+        size = sizeof(struct kvm_tdx_capabilities) +
+               nr_cpuid_configs * sizeof(struct kvm_tdx_cpuid_config);
+        caps = g_malloc0(size);
+        caps->nr_cpuid_configs = nr_cpuid_configs;
+
+        r = tdx_vm_ioctl(KVM_TDX_CAPABILITIES, 0, caps);
+        if (r == -E2BIG) {
+            g_free(caps);
+            nr_cpuid_configs *= 2;
+            if (nr_cpuid_configs > KVM_MAX_CPUID_ENTRIES) {
+                error_setg(errp, "%s: KVM TDX seems broken that number of CPUID "
+                           "entries in kvm_tdx_capabilities exceeds limit %d",
+                           __func__, KVM_MAX_CPUID_ENTRIES);
+                return r;
+            }
+        } else if (r < 0) {
+            g_free(caps);
+            error_setg_errno(errp, -r, "%s: KVM_TDX_CAPABILITIES failed", __func__);
+            return r;
+        }
+    }
+    while (r == -E2BIG);
+
+    tdx_caps = caps;
+
+    return 0;
+}
+
 int tdx_kvm_init(MachineState *ms, Error **errp)
 {
+    int r = 0;
+
     ms->require_guest_memfd = true;
 
-    return 0;
+    if (!tdx_caps) {
+        r = get_tdx_capabilities(errp);
+    }
+
+    return r;
 }
 
 /* tdx guest */
-- 
2.34.1