igvm: fix build when igvm is not installed in a well known path

`stubs/igvm.c` includes `igvm-internal.h`, that in turn includes the igvm library.
This is required just for the QIgvm declaration and creates an
unnecessary dependency on the library.

Since igvm is not listed as a dependency of stubs, this results in build
failing when the library is not installed in a "well known" path of the
system.

Add a forward declaration for QIgvm and move the definition of
`qigvm_directive_madt` to `igvm.h` so that we can drop `igvm-internal.h` from
`stubs/igvm.c`.

Fixes: dea1f68a5c ("igvm: Fill MADT IGVM parameter field on x86_64")
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Luigi Leonardi <leonardi@redhat.com>
Message-ID: <20260309-master-v2-1-7e02f07a1096@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

include/qemu/typedefs.h

@@ -102,6 +102,7 @@ typedef struct QEMUSGList QEMUSGList;
 typedef struct QemuSpin QemuSpin;
 typedef struct QEMUTimer QEMUTimer;
 typedef struct QEMUTimerListGroup QEMUTimerListGroup;
+typedef struct QIgvm QIgvm;
 typedef struct QList QList;
 typedef struct QNull QNull;
 typedef struct QNum QNum;

include/system/igvm-internal.h

@@ -42,7 +42,7 @@ typedef struct QIgvmParameterData {
  * QIgvm contains the information required during processing of a single IGVM
  * file.
  */
-typedef struct QIgvm {
+struct QIgvm {
     IgvmHandle file;
     MachineState *machine_state;
     ConfidentialGuestSupportClass *cgsc;
@@ -67,16 +67,11 @@ typedef struct QIgvm {
     unsigned region_start_index;
     unsigned region_last_index;
     unsigned region_page_count;
-} QIgvm;
+};
 
 IgvmHandle qigvm_file_init(char *filename, Error **errp);
 
 QIgvmParameterData*
 qigvm_find_param_entry(QIgvm *igvm, uint32_t parameter_area_index);
 
-/*
- *  IGVM parameter handlers
- */
-int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data, Error **errp);
-
 #endif

include/system/igvm.h

@@ -27,4 +27,9 @@ int qigvm_x86_get_mem_map_entry(int index,
 int qigvm_x86_set_vp_context(void *data, int index,
                              Error **errp);
 
+/*
+ *  IGVM parameter handlers
+ */
+int qigvm_directive_madt(QIgvm *ctx, const uint8_t *header_data, Error **errp);
+
 #endif

stubs/igvm.c

@@ -12,7 +12,6 @@
 #include "qemu/osdep.h"
 
 #include "system/igvm.h"
-#include "system/igvm-internal.h"
 
 int qigvm_x86_get_mem_map_entry(int index,
                                 ConfidentialGuestMemoryMapEntry *entry,