xen: create xenstore areas for XenDevice-s

This patch adds a new source module, xen-bus-helper.c, which builds on
basic libxenstore primitives to provide functions to create (setting
permissions appropriately) and destroy xenstore areas, and functions to
'printf' and 'scanf' nodes therein. The main xen-bus code then uses
these primitives [1] to initialize and destroy the frontend and backend
areas for a XenDevice during realize and unrealize respectively.

The 'xen-block' implementation is extended with a 'get_name' method that
returns the VBD number. This number is required to 'name' the xenstore
areas.

NOTE: An exit handler is also added to make sure the xenstore areas are
      cleaned up if QEMU terminates without devices being unrealized.

[1] The 'scanf' functions are actually not yet needed, but they will be
    needed by code delivered in subsequent patches.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>

1 files changed, 319 insertions, 2 deletions

diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index bc04da748b..843fda26a9 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -8,24 +8,102 @@
 #include "qemu/osdep.h"
 #include "hw/hw.h"
 #include "hw/sysbus.h"
+#include "hw/xen/xen.h"
 #include "hw/xen/xen-bus.h"
+#include "hw/xen/xen-bus-helper.h"
+#include "monitor/monitor.h"
 #include "qapi/error.h"
+#include "sysemu/sysemu.h"
 #include "trace.h"
 
+static char *xen_device_get_backend_path(XenDevice *xendev)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
+    const char *type = object_get_typename(OBJECT(xendev));
+    const char *backend = xendev_class->backend;
+
+    if (!backend) {
+        backend = type;
+    }
+
+    return g_strdup_printf("/local/domain/%u/backend/%s/%u/%s",
+                           xenbus->backend_id, backend, xendev->frontend_id,
+                           xendev->name);
+}
+
+static char *xen_device_get_frontend_path(XenDevice *xendev)
+{
+    XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
+    const char *type = object_get_typename(OBJECT(xendev));
+    const char *device = xendev_class->device;
+
+    if (!device) {
+        device = type;
+    }
+
+    return g_strdup_printf("/local/domain/%u/device/%s/%s",
+                           xendev->frontend_id, device, xendev->name);
+}
+
+static void xen_bus_print_dev(Monitor *mon, DeviceState *dev, int indent)
+{
+    XenDevice *xendev = XEN_DEVICE(dev);
+
+    monitor_printf(mon, "%*sname = '%s' frontend_id = %u\n",
+                   indent, "", xendev->name, xendev->frontend_id);
+}
+
+static char *xen_bus_get_dev_path(DeviceState *dev)
+{
+    return xen_device_get_backend_path(XEN_DEVICE(dev));
+}
+
 static void xen_bus_unrealize(BusState *bus, Error **errp)
 {
+    XenBus *xenbus = XEN_BUS(bus);
+
     trace_xen_bus_unrealize();
+
+    if (!xenbus->xsh) {
+        return;
+    }
+
+    xs_close(xenbus->xsh);
 }
 
 static void xen_bus_realize(BusState *bus, Error **errp)
 {
+    XenBus *xenbus = XEN_BUS(bus);
+    unsigned int domid;
+
     trace_xen_bus_realize();
+
+    xenbus->xsh = xs_open(0);
+    if (!xenbus->xsh) {
+        error_setg_errno(errp, errno, "failed xs_open");
+        goto fail;
+    }
+
+    if (xs_node_scanf(xenbus->xsh, XBT_NULL, "", /* domain root node */
+                      "domid", NULL, "%u", &domid) == 1) {
+        xenbus->backend_id = domid;
+    } else {
+        xenbus->backend_id = 0; /* Assume lack of node means dom0 */
+    }
+
+    return;
+
+fail:
+    xen_bus_unrealize(bus, &error_abort);
 }
 
 static void xen_bus_class_init(ObjectClass *class, void *data)
 {
     BusClass *bus_class = BUS_CLASS(class);
 
+    bus_class->print_dev = xen_bus_print_dev;
+    bus_class->get_dev_path = xen_bus_get_dev_path;
     bus_class->realize = xen_bus_realize;
     bus_class->unrealize = xen_bus_unrealize;
 }
@@ -42,27 +120,241 @@ static const TypeInfo xen_bus_type_info = {
     },
 };
 
+static void xen_device_backend_printf(XenDevice *xendev, const char *key,
+                                      const char *fmt, ...)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    Error *local_err = NULL;
+    va_list ap;
+
+    g_assert(xenbus->xsh);
+
+    va_start(ap, fmt);
+    xs_node_vprintf(xenbus->xsh, XBT_NULL, xendev->backend_path, key,
+                    &local_err, fmt, ap);
+    va_end(ap);
+
+    if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
+static void xen_device_backend_set_state(XenDevice *xendev,
+                                         enum xenbus_state state)
+{
+    const char *type = object_get_typename(OBJECT(xendev));
+
+    if (xendev->backend_state == state) {
+        return;
+    }
+
+    trace_xen_device_backend_state(type, xendev->name,
+                                   xs_strstate(state));
+
+    xendev->backend_state = state;
+    xen_device_backend_printf(xendev, "state", "%u", state);
+}
+
+static void xen_device_backend_create(XenDevice *xendev, Error **errp)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    struct xs_permissions perms[2];
+    Error *local_err = NULL;
+
+    xendev->backend_path = xen_device_get_backend_path(xendev);
+
+    perms[0].id = xenbus->backend_id;
+    perms[0].perms = XS_PERM_NONE;
+    perms[1].id = xendev->frontend_id;
+    perms[1].perms = XS_PERM_READ;
+
+    g_assert(xenbus->xsh);
+
+    xs_node_create(xenbus->xsh, XBT_NULL, xendev->backend_path, perms,
+                   ARRAY_SIZE(perms), &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "failed to create backend: ");
+    }
+}
+
+static void xen_device_backend_destroy(XenDevice *xendev)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    Error *local_err = NULL;
+
+    if (!xendev->backend_path) {
+        return;
+    }
+
+    g_assert(xenbus->xsh);
+
+    xs_node_destroy(xenbus->xsh, XBT_NULL, xendev->backend_path,
+                    &local_err);
+    g_free(xendev->backend_path);
+    xendev->backend_path = NULL;
+
+    if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
+static void xen_device_frontend_printf(XenDevice *xendev, const char *key,
+                                       const char *fmt, ...)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    Error *local_err = NULL;
+    va_list ap;
+
+    g_assert(xenbus->xsh);
+
+    va_start(ap, fmt);
+    xs_node_vprintf(xenbus->xsh, XBT_NULL, xendev->frontend_path, key,
+                    &local_err, fmt, ap);
+    va_end(ap);
+
+    if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
+static void xen_device_frontend_set_state(XenDevice *xendev,
+                                          enum xenbus_state state)
+{
+    const char *type = object_get_typename(OBJECT(xendev));
+
+    if (xendev->frontend_state == state) {
+        return;
+    }
+
+    trace_xen_device_frontend_state(type, xendev->name,
+                                    xs_strstate(state));
+
+    xendev->frontend_state = state;
+    xen_device_frontend_printf(xendev, "state", "%u", state);
+}
+
+static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    struct xs_permissions perms[2];
+    Error *local_err = NULL;
+
+    xendev->frontend_path = xen_device_get_frontend_path(xendev);
+
+    perms[0].id = xendev->frontend_id;
+    perms[0].perms = XS_PERM_NONE;
+    perms[1].id = xenbus->backend_id;
+    perms[1].perms = XS_PERM_READ | XS_PERM_WRITE;
+
+    g_assert(xenbus->xsh);
+
+    xs_node_create(xenbus->xsh, XBT_NULL, xendev->frontend_path, perms,
+                   ARRAY_SIZE(perms), &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "failed to create frontend: ");
+    }
+}
+
+static void xen_device_frontend_destroy(XenDevice *xendev)
+{
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+    Error *local_err = NULL;
+
+    if (!xendev->frontend_path) {
+        return;
+    }
+
+    g_assert(xenbus->xsh);
+
+    xs_node_destroy(xenbus->xsh, XBT_NULL, xendev->frontend_path,
+                    &local_err);
+    g_free(xendev->frontend_path);
+    xendev->frontend_path = NULL;
+
+    if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
 static void xen_device_unrealize(DeviceState *dev, Error **errp)
 {
     XenDevice *xendev = XEN_DEVICE(dev);
     XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
     const char *type = object_get_typename(OBJECT(xendev));
 
-    trace_xen_device_unrealize(type);
+    if (!xendev->name) {
+        return;
+    }
+
+    trace_xen_device_unrealize(type, xendev->name);
+
+    if (xendev->exit.notify) {
+        qemu_remove_exit_notifier(&xendev->exit);
+        xendev->exit.notify = NULL;
+    }
 
     if (xendev_class->unrealize) {
         xendev_class->unrealize(xendev, errp);
     }
+
+    xen_device_frontend_destroy(xendev);
+    xen_device_backend_destroy(xendev);
+
+    g_free(xendev->name);
+    xendev->name = NULL;
+}
+
+static void xen_device_exit(Notifier *n, void *data)
+{
+    XenDevice *xendev = container_of(n, XenDevice, exit);
+
+    xen_device_unrealize(DEVICE(xendev), &error_abort);
 }
 
 static void xen_device_realize(DeviceState *dev, Error **errp)
 {
     XenDevice *xendev = XEN_DEVICE(dev);
     XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
+    XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
     const char *type = object_get_typename(OBJECT(xendev));
     Error *local_err = NULL;
 
-    trace_xen_device_realize(type);
+    if (xendev->frontend_id == DOMID_INVALID) {
+        xendev->frontend_id = xen_domid;
+    }
+
+    if (xendev->frontend_id >= DOMID_FIRST_RESERVED) {
+        error_setg(errp, "invalid frontend-id");
+        goto unrealize;
+    }
+
+    if (!xendev_class->get_name) {
+        error_setg(errp, "get_name method not implemented");
+        goto unrealize;
+    }
+
+    xendev->name = xendev_class->get_name(xendev, &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "failed to get device name: ");
+        goto unrealize;
+    }
+
+    trace_xen_device_realize(type, xendev->name);
+
+    xen_device_backend_create(xendev, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto unrealize;
+    }
+
+    xen_device_frontend_create(xendev, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto unrealize;
+    }
 
     if (xendev_class->realize) {
         xendev_class->realize(xendev, &local_err);
@@ -72,18 +364,43 @@ static void xen_device_realize(DeviceState *dev, Error **errp)
         }
     }
 
+    xen_device_backend_printf(xendev, "frontend", "%s",
+                              xendev->frontend_path);
+    xen_device_backend_printf(xendev, "frontend-id", "%u",
+                              xendev->frontend_id);
+    xen_device_backend_printf(xendev, "online", "%u", 1);
+    xen_device_backend_printf(xendev, "hotplug-status", "connected");
+
+    xen_device_backend_set_state(xendev, XenbusStateInitWait);
+
+    xen_device_frontend_printf(xendev, "backend", "%s",
+                               xendev->backend_path);
+    xen_device_frontend_printf(xendev, "backend-id", "%u",
+                               xenbus->backend_id);
+
+    xen_device_frontend_set_state(xendev, XenbusStateInitialising);
+
+    xendev->exit.notify = xen_device_exit;
+    qemu_add_exit_notifier(&xendev->exit);
     return;
 
 unrealize:
     xen_device_unrealize(dev, &error_abort);
 }
 
+static Property xen_device_props[] = {
+    DEFINE_PROP_UINT16("frontend-id", XenDevice, frontend_id,
+                       DOMID_INVALID),
+    DEFINE_PROP_END_OF_LIST()
+};
+
 static void xen_device_class_init(ObjectClass *class, void *data)
 {
     DeviceClass *dev_class = DEVICE_CLASS(class);
 
     dev_class->realize = xen_device_realize;
     dev_class->unrealize = xen_device_unrealize;
+    dev_class->props = xen_device_props;
     dev_class->bus_type = TYPE_XEN_BUS;
 }