i386/tdx: handle TDG.VP.VMCALL<GetTdVmCallInfo>

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/kvm/kvm.c

@@ -6170,6 +6170,18 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
             break;
         }
         break;
+    case KVM_EXIT_TDX:
+        /*
+         * run->tdx is already set up for the case where userspace
+         * does not handle the TDVMCALL.
+         */
+        switch (run->tdx.nr) {
+        case TDVMCALL_GET_TD_VM_CALL_INFO:
+            tdx_handle_get_tdvmcall_info(cpu, run);
+            break;
+        }
+        ret = 0;
+        break;
     default:
         fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
         ret = -1;

target/i386/kvm/tdx-stub.c

@@ -18,3 +18,7 @@ int tdx_handle_report_fatal_error(X86CPU *cpu, struct kvm_run *run)
 {
     return -EINVAL;
 }
+
+void tdx_handle_get_tdvmcall_info(X86CPU *cpu, struct kvm_run *run)
+{
+}

target/i386/kvm/tdx.c

@@ -1120,6 +1120,18 @@ int tdx_parse_tdvf(void *flash_ptr, int size)
     return tdvf_parse_metadata(&tdx_guest->tdvf, flash_ptr, size);
 }
 
+void tdx_handle_get_tdvmcall_info(X86CPU *cpu, struct kvm_run *run)
+{
+    if (run->tdx.get_tdvmcall_info.leaf != 1) {
+	return;
+    }
+
+    run->tdx.get_tdvmcall_info.r11 = 0;
+    run->tdx.get_tdvmcall_info.r12 = 0;
+    run->tdx.get_tdvmcall_info.r13 = 0;
+    run->tdx.get_tdvmcall_info.r14 = 0;
+}
+
 static void tdx_panicked_on_fatal_error(X86CPU *cpu, uint64_t error_code,
                                         char *message, uint64_t gpa)
 {

target/i386/kvm/tdx.h

@@ -21,6 +21,14 @@ typedef struct TdxGuestClass {
 /* TDX requires bus frequency 25MHz */
 #define TDX_APIC_BUS_CYCLES_NS 40
 
+#define TDVMCALL_GET_TD_VM_CALL_INFO    0x10000
+
+#define TDG_VP_VMCALL_SUCCESS           0x0000000000000000ULL
+#define TDG_VP_VMCALL_RETRY             0x0000000000000001ULL
+#define TDG_VP_VMCALL_INVALID_OPERAND   0x8000000000000000ULL
+#define TDG_VP_VMCALL_GPA_INUSE         0x8000000000000001ULL
+#define TDG_VP_VMCALL_ALIGN_ERROR       0x8000000000000002ULL
+
 enum TdxRamType {
     TDX_RAM_UNACCEPTED,
     TDX_RAM_ADDED,
@@ -61,5 +69,6 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp);
 void tdx_set_tdvf_region(MemoryRegion *tdvf_mr);
 int tdx_parse_tdvf(void *flash_ptr, int size);
 int tdx_handle_report_fatal_error(X86CPU *cpu, struct kvm_run *run);
+void tdx_handle_get_tdvmcall_info(X86CPU *cpu, struct kvm_run *run);
 
 #endif /* QEMU_I386_TDX_H */