[Qemu-devel] [PATCH 1/9] qdev/qbus: Add hidden device support

[Jens Freimann]

This adds support for hiding a device to the qbus and qdev APIs.
qdev_device_add() is modified to check for a standby argument in the
option string. A DeviceListener callback should_be_hidden() is added. It
can be used by a standby device to inform qdev that this device should
not be added now. The standby device handler can store the device
options to plug the device in at a later point in time.

Signed-off-by: Jens Freimann <address@hidden>
---
 hw/core/qdev.c         | 19 +++++++++++++++++++
 hw/vfio/pci.c          |  1 +
 hw/vfio/pci.h          |  1 +
 include/hw/qdev-core.h |  8 ++++++++
 qdev-monitor.c         | 43 ++++++++++++++++++++++++++++++++++++++----
 vl.c                   |  6 ++++--
 6 files changed, 72 insertions(+), 6 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 94ebc0a4a1..31e90ebaa2 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -211,6 +211,25 @@ void device_listener_unregister(DeviceListener *listener)
     QTAILQ_REMOVE(&device_listeners, listener, link);
 }
 
+bool qdev_should_hide_device(QemuOpts *opts, Error **errp)
+{
+    bool res = false;
+    bool match_found = false;
+
+    DeviceListener *listener;
+
+    QTAILQ_FOREACH(listener, &device_listeners, link) {
+       if (listener->should_be_hidden) {
+            listener->should_be_hidden(listener, opts, &match_found, &res);
+        }
+
+        if (match_found) {
+            break;
+        }
+    }
+    return res;
+}
+
 void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
                                  int required_for_version)
 {
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index d7a4e1875c..d6ae9bd4ac 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3105,6 +3105,7 @@ static Property vfio_pci_dev_properties[] = {
                             display, ON_OFF_AUTO_OFF),
     DEFINE_PROP_UINT32("xres", VFIOPCIDevice, display_xres, 0),
     DEFINE_PROP_UINT32("yres", VFIOPCIDevice, display_yres, 0),
+    DEFINE_PROP_STRING("standby", VFIOPCIDevice, standby),
     DEFINE_PROP_UINT32("x-intx-mmap-timeout-ms", VFIOPCIDevice,
                        intx.mmap_timeout, 1100),
     DEFINE_PROP_BIT("x-vga", VFIOPCIDevice, features,
diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index 834a90d646..27d58fc55b 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -134,6 +134,7 @@ typedef struct VFIOPCIDevice {
     PCIHostDeviceAddress host;
     EventNotifier err_notifier;
     EventNotifier req_notifier;
+    char *standby;
     int (*resetfn)(struct VFIOPCIDevice *);
     uint32_t vendor_id;
     uint32_t device_id;
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 136df7774c..6174538b01 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -158,6 +158,13 @@ struct DeviceState {
 struct DeviceListener {
     void (*realize)(DeviceListener *listener, DeviceState *dev);
     void (*unrealize)(DeviceListener *listener, DeviceState *dev);
+    /*
+     * This callback is called just upon init of the DeviceState
+     * and can be used by a standby device for informing qdev if this
+     * device should be hidden by checking the device opts
+     */
+    void (*should_be_hidden)(DeviceListener *listener, QemuOpts *device_opts,
+            bool *match_found, bool *res);
     QTAILQ_ENTRY(DeviceListener) link;
 };
 
@@ -457,5 +464,6 @@ void device_listener_unregister(DeviceListener *listener);
 VMChangeStateEntry *qdev_add_vm_change_state_handler(DeviceState *dev,
                                                      VMChangeStateHandler *cb,
                                                      void *opaque);
+bool qdev_should_hide_device(QemuOpts *opts, Error **errp);
 
 #endif
diff --git a/qdev-monitor.c b/qdev-monitor.c
index 58222c2211..c69e283419 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -32,8 +32,10 @@
 #include "qemu/help_option.h"
 #include "qemu/option.h"
 #include "qemu/qemu-print.h"
+#include "qemu/option_int.h"
 #include "sysemu/block-backend.h"
 #include "migration/misc.h"
+#include "migration/migration.h"
 
 /*
  * Aliases were a bad idea from the start.  Let's keep them
@@ -561,14 +563,45 @@ void qdev_set_id(DeviceState *dev, const char *id)
     }
 }
 
+static int is_failover_device(void *opaque, const char *name, const char 
*value,
+                        Error **errp)
+{
+    if (strcmp(name, "standby") == 0) {
+        QemuOpts *opts = (QemuOpts *)opaque;
+
+        if (qdev_should_hide_device(opts, errp) && errp && !*errp) {
+            return 1;
+        } else if (errp && *errp) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static bool should_hide_device(QemuOpts *opts, Error **err)
+{
+    if (qemu_opt_foreach(opts, is_failover_device, opts, err) == 0) {
+        return false;
+    }
+    return true;
+}
+
 DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
 {
     DeviceClass *dc;
     const char *driver, *path;
-    DeviceState *dev;
+    DeviceState *dev = NULL;
     BusState *bus = NULL;
     Error *err = NULL;
 
+    if (opts && should_hide_device(opts, &err)) {
+        if (err) {
+            goto err_del_dev;
+        }
+        return NULL;
+    }
+
     driver = qemu_opt_get(opts, "driver");
     if (!driver) {
         error_setg(errp, QERR_MISSING_PARAMETER, "driver");
@@ -640,8 +673,10 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
 
 err_del_dev:
     error_propagate(errp, err);
-    object_unparent(OBJECT(dev));
-    object_unref(OBJECT(dev));
+    if (dev) {
+        object_unparent(OBJECT(dev));
+        object_unref(OBJECT(dev));
+    }
     return NULL;
 }
 
@@ -810,7 +845,7 @@ void qdev_unplug(DeviceState *dev, Error **errp)
         return;
     }
 
-    if (!migration_is_idle()) {
+    if (!migration_is_idle() && !migration_in_setup(migrate_get_current())) {
         error_setg(errp, "device_del not allowed while migrating");
         return;
     }
diff --git a/vl.c b/vl.c
index b426b32134..1848195da7 100644
--- a/vl.c
+++ b/vl.c
@@ -2189,10 +2189,12 @@ static int device_init_func(void *opaque, QemuOpts 
*opts, Error **errp)
     DeviceState *dev;
 
     dev = qdev_device_add(opts, errp);
-    if (!dev) {
+    if (!dev && *errp) {
+        error_report_err(*errp);
         return -1;
+    } else if (dev) {
+        object_unref(OBJECT(dev));
     }
-    object_unref(OBJECT(dev));
     return 0;
 }
 
-- 
2.21.0