vfio: Add Error** argument to .set_dirty_page_tracking() handler

We will use the Error object to improve error reporting in the
.log_global*() handlers of VFIO. Add documentation while at it.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/common.c

@@ -1076,7 +1076,7 @@ static bool vfio_listener_log_global_start(MemoryListener *listener,
     if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
         ret = vfio_devices_dma_logging_start(bcontainer);
     } else {
-        ret = vfio_container_set_dirty_page_tracking(bcontainer, true);
+        ret = vfio_container_set_dirty_page_tracking(bcontainer, true, NULL);
     }
 
     if (ret) {
@@ -1096,7 +1096,7 @@ static void vfio_listener_log_global_stop(MemoryListener *listener)
     if (vfio_devices_all_device_dirty_tracking(bcontainer)) {
         vfio_devices_dma_logging_stop(bcontainer);
     } else {
-        ret = vfio_container_set_dirty_page_tracking(bcontainer, false);
+        ret = vfio_container_set_dirty_page_tracking(bcontainer, false, NULL);
     }
 
     if (ret) {

hw/vfio/container-base.c

@@ -53,14 +53,14 @@ void vfio_container_del_section_window(VFIOContainerBase *bcontainer,
 }
 
 int vfio_container_set_dirty_page_tracking(VFIOContainerBase *bcontainer,
-                                           bool start)
+                                           bool start, Error **errp)
 {
     if (!bcontainer->dirty_pages_supported) {
         return 0;
     }
 
     g_assert(bcontainer->ops->set_dirty_page_tracking);
-    return bcontainer->ops->set_dirty_page_tracking(bcontainer, start);
+    return bcontainer->ops->set_dirty_page_tracking(bcontainer, start, errp);
 }
 
 int vfio_container_query_dirty_bitmap(const VFIOContainerBase *bcontainer,

hw/vfio/container.c

@@ -209,7 +209,7 @@ static int vfio_legacy_dma_map(const VFIOContainerBase *bcontainer, hwaddr iova,
 
 static int
 vfio_legacy_set_dirty_page_tracking(const VFIOContainerBase *bcontainer,
-                                    bool start)
+                                    bool start, Error **errp)
 {
     const VFIOContainer *container = container_of(bcontainer, VFIOContainer,
                                                   bcontainer);
@@ -227,8 +227,8 @@ vfio_legacy_set_dirty_page_tracking(const VFIOContainerBase *bcontainer,
     ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, &dirty);
     if (ret) {
         ret = -errno;
-        error_report("Failed to set dirty tracking flag 0x%x errno: %d",
+        error_setg_errno(errp, errno, "Failed to set dirty tracking flag 0x%x",
-                     dirty.flags, errno);
+                         dirty.flags);
     }
 
     return ret;

include/hw/vfio/vfio-container-base.h

@@ -82,7 +82,7 @@ int vfio_container_add_section_window(VFIOContainerBase *bcontainer,
 void vfio_container_del_section_window(VFIOContainerBase *bcontainer,
                                        MemoryRegionSection *section);
 int vfio_container_set_dirty_page_tracking(VFIOContainerBase *bcontainer,
-                                           bool start);
+                                           bool start, Error **errp);
 int vfio_container_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
                                       VFIOBitmap *vbmap,
                                       hwaddr iova, hwaddr size);
@@ -121,9 +121,23 @@ struct VFIOIOMMUClass {
     int (*attach_device)(const char *name, VFIODevice *vbasedev,
                          AddressSpace *as, Error **errp);
     void (*detach_device)(VFIODevice *vbasedev);
+
     /* migration feature */
+
+    /**
+     * @set_dirty_page_tracking
+     *
+     * Start or stop dirty pages tracking on VFIO container
+     *
+     * @bcontainer: #VFIOContainerBase on which to de/activate dirty
+     *              page tracking
+     * @start: indicates whether to start or stop dirty pages tracking
+     * @errp: pointer to Error*, to store an error if it happens.
+     *
+     * Returns zero to indicate success and negative for error
+     */
     int (*set_dirty_page_tracking)(const VFIOContainerBase *bcontainer,
-                                   bool start);
+                                   bool start, Error **errp);
     int (*query_dirty_bitmap)(const VFIOContainerBase *bcontainer,
                               VFIOBitmap *vbmap,
                               hwaddr iova, hwaddr size);