migration: vfio cpr state hook

Define a list of vfio devices in CPR state, in a subsection so that
older QEMU can be live updated to this version.  However, new QEMU
will not be live updateable to old QEMU.  This is acceptable because
CPR is not yet commonly used, and updates to older versions are unusual.

The contents of each device object will be defined by the vfio subsystem
in a subsequent patch.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-14-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/cpr-iommufd.c

@@ -14,6 +14,8 @@
 #include "system/iommufd.h"
 #include "vfio-iommufd.h"
 
+const VMStateDescription vmstate_cpr_vfio_devices;  /* TBD in a later patch */
+
 static bool vfio_cpr_supported(IOMMUFDBackend *be, Error **errp)
 {
     if (!iommufd_change_process_capable(be)) {

hw/vfio/iommufd-stubs.c

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "migration/cpr.h"
+#include "migration/vmstate.h"
+
+const VMStateDescription vmstate_cpr_vfio_devices = {
+    .name = CPR_STATE "/vfio devices",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (const VMStateField[]){
+        VMSTATE_END_OF_LIST()
+    }
+};

hw/vfio/meson.build

@@ -33,6 +33,7 @@ system_ss.add(when: ['CONFIG_VFIO', 'CONFIG_IOMMUFD'], if_true: files(
   'iommufd.c',
   'cpr-iommufd.c',
 ))
+system_ss.add(when: 'CONFIG_IOMMUFD', if_false: files('iommufd-stubs.c'))
 system_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
   'display.c',
 ))

include/hw/vfio/vfio-cpr.h

@@ -75,6 +75,7 @@ void vfio_cpr_delete_vector_fd(struct VFIOPCIDevice *vdev, const char *name,
                                int nr);
 
 extern const VMStateDescription vfio_cpr_pci_vmstate;
+extern const VMStateDescription vmstate_cpr_vfio_devices;
 
 void vfio_cpr_add_kvm_notifier(void);
 

include/migration/cpr.h

@@ -9,11 +9,23 @@
 #define MIGRATION_CPR_H
 
 #include "qapi/qapi-types-migration.h"
+#include "qemu/queue.h"
 
 #define MIG_MODE_NONE           -1
 
 #define QEMU_CPR_FILE_MAGIC     0x51435052
 #define QEMU_CPR_FILE_VERSION   0x00000001
+#define CPR_STATE "CprState"
+
+typedef QLIST_HEAD(CprFdList, CprFd) CprFdList;
+typedef QLIST_HEAD(CprVFIODeviceList, CprVFIODevice) CprVFIODeviceList;
+
+typedef struct CprState {
+    CprFdList fds;
+    CprVFIODeviceList vfio_devices;
+} CprState;
+
+extern CprState cpr_state;
 
 void cpr_save_fd(const char *name, int id, int fd);
 void cpr_delete_fd(const char *name, int id);

migration/cpr.c

@@ -7,6 +7,7 @@
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
+#include "hw/vfio/vfio-device.h"
 #include "migration/cpr.h"
 #include "migration/misc.h"
 #include "migration/options.h"
@@ -20,13 +21,7 @@
 /*************************************************************************/
 /* cpr state container for all information to be saved. */
 
-typedef QLIST_HEAD(CprFdList, CprFd) CprFdList;
-
-typedef struct CprState {
-    CprFdList fds;
-} CprState;
-
-static CprState cpr_state;
+CprState cpr_state;
 
 /****************************************************************************/
 
@@ -127,8 +122,6 @@ int cpr_open_fd(const char *path, int flags, const char *name, int id,
 }
 
 /*************************************************************************/
-#define CPR_STATE "CprState"
-
 static const VMStateDescription vmstate_cpr_state = {
     .name = CPR_STATE,
     .version_id = 1,
@@ -136,6 +129,10 @@ static const VMStateDescription vmstate_cpr_state = {
     .fields = (VMStateField[]) {
         VMSTATE_QLIST_V(fds, CprState, 1, vmstate_cpr_fd, CprFd, next),
         VMSTATE_END_OF_LIST()
+    },
+    .subsections = (const VMStateDescription * const []) {
+        &vmstate_cpr_vfio_devices,
+        NULL
     }
 };
 /*************************************************************************/