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Subject[PATCH v2 04/18] xen/pvcalls: xenbus state handling
Date
Introduce the code to handle xenbus state changes.

Implement the probe function for the pvcalls backend. Write the
supported versions, max-page-order and function-calls nodes to xenstore,
as required by the protocol.

Introduce stub functions for disconnecting/connecting to a frontend.

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
---
drivers/xen/pvcalls-back.c | 135 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 135 insertions(+)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index 9044cf2..b4da138 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -25,20 +25,155 @@
#include <xen/xenbus.h>
#include <xen/interface/io/pvcalls.h>

+#define PVCALLS_VERSIONS "1"
+#define MAX_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
+
struct pvcalls_back_global {
struct list_head frontends;
struct semaphore frontends_lock;
} pvcalls_back_global;

+static int backend_connect(struct xenbus_device *dev)
+{
+ return 0;
+}
+
+static int backend_disconnect(struct xenbus_device *dev)
+{
+ return 0;
+}
+
static int pvcalls_back_probe(struct xenbus_device *dev,
const struct xenbus_device_id *id)
{
+ int err;
+
+ err = xenbus_printf(XBT_NIL, dev->nodename, "versions", "%s",
+ PVCALLS_VERSIONS);
+ if (err) {
+ pr_warn("%s write out 'version' failed\n", __func__);
+ return -EINVAL;
+ }
+
+ err = xenbus_printf(XBT_NIL, dev->nodename, "max-page-order", "%u",
+ MAX_RING_ORDER);
+ if (err) {
+ pr_warn("%s write out 'max-page-order' failed\n", __func__);
+ return err;
+ }
+
+ /* "1" means socket, connect, release, bind, listen, accept and poll*/
+ err = xenbus_printf(XBT_NIL, dev->nodename, "function-calls",
+ XENBUS_FUNCTIONS_CALLS);
+ if (err) {
+ pr_warn("%s write out 'function-calls' failed\n", __func__);
+ return err;
+ }
+
+ err = xenbus_switch_state(dev, XenbusStateInitWait);
+ if (err)
+ return err;
+
return 0;
}

+static void set_backend_state(struct xenbus_device *dev,
+ enum xenbus_state state)
+{
+ while (dev->state != state) {
+ switch (dev->state) {
+ case XenbusStateClosed:
+ switch (state) {
+ case XenbusStateInitWait:
+ case XenbusStateConnected:
+ xenbus_switch_state(dev, XenbusStateInitWait);
+ break;
+ case XenbusStateClosing:
+ xenbus_switch_state(dev, XenbusStateClosing);
+ break;
+ default:
+ __WARN();
+ }
+ break;
+ case XenbusStateInitWait:
+ case XenbusStateInitialised:
+ switch (state) {
+ case XenbusStateConnected:
+ backend_connect(dev);
+ xenbus_switch_state(dev, XenbusStateConnected);
+ break;
+ case XenbusStateClosing:
+ case XenbusStateClosed:
+ xenbus_switch_state(dev, XenbusStateClosing);
+ break;
+ default:
+ __WARN();
+ }
+ break;
+ case XenbusStateConnected:
+ switch (state) {
+ case XenbusStateInitWait:
+ case XenbusStateClosing:
+ case XenbusStateClosed:
+ down(&pvcalls_back_global.frontends_lock);
+ backend_disconnect(dev);
+ up(&pvcalls_back_global.frontends_lock);
+ xenbus_switch_state(dev, XenbusStateClosing);
+ break;
+ default:
+ __WARN();
+ }
+ break;
+ case XenbusStateClosing:
+ switch (state) {
+ case XenbusStateInitWait:
+ case XenbusStateConnected:
+ case XenbusStateClosed:
+ xenbus_switch_state(dev, XenbusStateClosed);
+ break;
+ default:
+ __WARN();
+ }
+ break;
+ default:
+ __WARN();
+ }
+ }
+}
+
static void pvcalls_back_changed(struct xenbus_device *dev,
enum xenbus_state frontend_state)
{
+ switch (frontend_state) {
+ case XenbusStateInitialising:
+ set_backend_state(dev, XenbusStateInitWait);
+ break;
+
+ case XenbusStateInitialised:
+ case XenbusStateConnected:
+ set_backend_state(dev, XenbusStateConnected);
+ break;
+
+ case XenbusStateClosing:
+ set_backend_state(dev, XenbusStateClosing);
+ break;
+
+ case XenbusStateClosed:
+ set_backend_state(dev, XenbusStateClosed);
+ if (xenbus_dev_is_online(dev))
+ break;
+ device_unregister(&dev->dev);
+ break;
+ case XenbusStateUnknown:
+ set_backend_state(dev, XenbusStateClosed);
+ device_unregister(&dev->dev);
+ break;
+
+ default:
+ xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+ frontend_state);
+ break;
+ }
}

static int pvcalls_back_remove(struct xenbus_device *dev)
--
1.9.1
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