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, 9 insertions, 0 deletions

diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index 8e78b6a..d27a286 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -13,6 +13,14 @@
 #include "hw/xen/xen-block.h"
 #include "trace.h"
 
+static char *xen_block_get_name(XenDevice *xendev, Error **errp)
+{
+    XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
+    XenBlockVdev *vdev = &blockdev->props.vdev;
+
+    return g_strdup_printf("%lu", vdev->number);
+}
+
 static void xen_block_unrealize(XenDevice *xendev, Error **errp)
 {
     XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
@@ -262,6 +270,7 @@ static void xen_block_class_init(ObjectClass *class, void *data)
     DeviceClass *dev_class = DEVICE_CLASS(class);
     XenDeviceClass *xendev_class = XEN_DEVICE_CLASS(class);
 
+    xendev_class->get_name = xen_block_get_name;
     xendev_class->realize = xen_block_realize;
     xendev_class->unrealize = xen_block_unrealize;