[PATCH] Convert balloon driver to xenstore

[Dan Smith <danms@us.ibm.com>]

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The attached patch converts the balloon driver and xend to use
xenstore instead of control messages.

Note: Because there is no way to set a watch on a non-existent key,
this patch includes a workaround to account for the fact that dom0's
store keys are not initialized by the tools before it boots.

Signed-off-by: Dan Smith <danms@us.ibm.com>


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diff -r 0db6a59abb95 -r b3ead8c9affb linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c
--- a/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c	Mon Aug  1 10:48:24 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c	Mon Aug  1 17:03:55 2005
@@ -5,6 +5,7 @@
  *
  * Copyright (c) 2003, B Dragovic
  * Copyright (c) 2003-2004, M Williamson, K Fraser
+ * Copyright (c) 2005 Dan M. Smith, IBM Corporation
  * 
  * This file may be distributed separately from the Linux kernel, or
  * incorporated into other software packages, subject to the following license:
@@ -42,7 +43,6 @@
 #include <linux/vmalloc.h>
 #include <asm-xen/xen_proc.h>
 #include <asm-xen/hypervisor.h>
-#include <asm-xen/ctrl_if.h>
 #include <asm-xen/balloon.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
@@ -50,6 +50,10 @@
 #include <asm/tlb.h>
 #include <linux/list.h>
 
+#include<asm-xen/xenbus.h>
+
+#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
+
 static struct proc_dir_entry *balloon_pde;
 
 static DECLARE_MUTEX(balloon_mutex);
@@ -77,11 +81,17 @@
 static DECLARE_WORK(balloon_worker, balloon_process, NULL);
 static struct timer_list balloon_timer;
 
+/* Flag for dom0 xenstore workaround */
+static int balloon_xenbus_init=0;
+
+/* Init Function */
+void balloon_init_watcher(void);
+
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)
 /* Use the private and mapping fields of struct page as a list. */
 #define PAGE_TO_LIST(p) ( (struct list_head *)&p->private )
 #define LIST_TO_PAGE(l) ( list_entry( ((unsigned long *)l),   \
-				      struct page, private ) )
+                                      struct page, private ) )
 #define UNLIST_PAGE(p)  do { list_del(PAGE_TO_LIST(p));       \
                              p->mapping = NULL;               \
                              p->private = 0; } while(0)
@@ -297,25 +307,96 @@
     schedule_work(&balloon_worker);
 }
 
-static void balloon_ctrlif_rx(ctrl_msg_t *msg, unsigned long id)
-{
-    switch ( msg->subtype )
-    {
-    case CMSG_MEM_REQUEST_SET:
-    {
-        mem_request_t *req = (mem_request_t *)&msg->msg[0];
-        set_new_target(req->target);
-        req->status = 0;
-    }
-    break;        
-
-    default:
-        msg->length = 0;
-        break;
-    }
-
-    ctrl_if_send_response(msg);
-}
+static struct xenbus_watch xb_watch =
+{
+    .node = "memory"
+};
+
+/* FIXME: This is part of a dom0 sequencing workaround */
+static struct xenbus_watch root_watch =
+{
+    .node = "/"
+};
+
+/* React to a change in the target key */
+static void watch_target(struct xenbus_watch *watch, const char *node)
+{
+    unsigned long new_target;
+    int err;
+
+    if(watch == &root_watch)
+    {
+        /* FIXME: This is part of a dom0 sequencing workaround */
+        if(register_xenbus_watch(&xb_watch) == 0)
+        {
+            /* 
+               We successfully set a watch on memory/target:
+               now we can stop watching root 
+            */
+            unregister_xenbus_watch(&root_watch);
+            balloon_xenbus_init=1;
+        } 
+        else 
+        {
+            return;
+        }
+    }
+
+    err = xenbus_scanf("memory", "target", "%lu", &new_target);
+        
+    if(err != 1) 
+    {
+        IPRINTK("Unable to read memory/target\n");
+        return;
+    } 
+        
+    set_new_target(new_target >> PAGE_SHIFT);
+    
+}
+
+/* 
+   Try to set up our watcher, if not already set
+   
+*/
+void balloon_init_watcher(void) 
+{
+    int err;
+
+    if(!xen_start_info.store_evtchn)
+    {
+        IPRINTK("Delaying watcher init until xenstore is available\n");
+        return;
+    }
+
+    down(&xenbus_lock);
+
+    if(! balloon_xenbus_init) 
+    {
+        err = register_xenbus_watch(&xb_watch);
+        if(err) 
+        {
+            /* BIG FAT FIXME: dom0 sequencing workaround
+             * dom0 can't set a watch on memory/target until
+             * after the tools create it.  So, we have to watch
+             * the whole store until that happens.
+             *
+             * This will go away when we have the ability to watch
+             * non-existant keys
+             */
+            register_xenbus_watch(&root_watch);
+        } 
+        else
+        {
+            IPRINTK("Balloon xenbus watcher initialized\n");
+            balloon_xenbus_init = 1;
+        }
+    }
+
+    up(&xenbus_lock);
+
+}
+
+EXPORT_SYMBOL(balloon_init_watcher);
 
 static int balloon_write(struct file *file, const char __user *buffer,
                          unsigned long count, void *data)
@@ -346,7 +427,6 @@
 {
     int len;
 
-#define K(_p) ((_p)<<(PAGE_SHIFT-10))
     len = sprintf(
         page,
         "Current allocation: %8lu kB\n"
@@ -354,13 +434,14 @@
         "Low-mem balloon:    %8lu kB\n"
         "High-mem balloon:   %8lu kB\n"
         "Xen hard limit:     ",
-        K(current_pages), K(target_pages), K(balloon_low), K(balloon_high));
+        PAGES2KB(current_pages), PAGES2KB(target_pages), 
+        PAGES2KB(balloon_low), PAGES2KB(balloon_high));
 
     if ( hard_limit != ~0UL )
         len += sprintf(
             page + len, 
             "%8lu kB (inc. %8lu kB driver headroom)\n",
-            K(hard_limit), K(driver_pages));
+            PAGES2KB(hard_limit), PAGES2KB(driver_pages));
     else
         len += sprintf(
             page + len,
@@ -396,9 +477,7 @@
 
     balloon_pde->read_proc  = balloon_read;
     balloon_pde->write_proc = balloon_write;
-
-    (void)ctrl_if_register_receiver(CMSG_MEM_REQUEST, balloon_ctrlif_rx, 0);
-
+    
     /* Initialise the balloon with excess memory space. */
     for ( pfn = xen_start_info.nr_pages; pfn < max_pfn; pfn++ )
     {
@@ -406,6 +485,11 @@
         if ( !PageReserved(page) )
             balloon_append(page);
     }
+
+    xb_watch.callback = watch_target;
+    root_watch.callback = watch_target;
+
+    balloon_init_watcher();
 
     return 0;
 }
diff -r 0db6a59abb95 -r b3ead8c9affb linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c	Mon Aug  1 10:48:24 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c	Mon Aug  1 17:03:55 2005
@@ -309,6 +309,9 @@
 		return err;
 	}
 
+	/* Initialize non-xenbus drivers */
+	balloon_init_watcher();
+
 	down(&xenbus_lock);
 	/* Enumerate devices in xenstore. */
 	xenbus_probe_devices("device");
diff -r 0db6a59abb95 -r b3ead8c9affb tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py	Mon Aug  1 10:48:24 2005
+++ b/tools/python/xen/xend/XendDomainInfo.py	Mon Aug  1 17:03:55 2005
@@ -152,6 +152,9 @@
         vm = cls(db)
         vm.construct(config)
         vm.saveToDB(sync=True)
+        # Flush info to xenstore immediately
+        vm.exportToDB()
+
         return vm
 
     create = classmethod(create)
@@ -172,6 +175,7 @@
         log.debug('config=' + prettyprintstring(config))
 
         vm.memory = info['mem_kb']/1024
+        vm.target = info['mem_kb'] * 1024
 
         if config:
             try:
@@ -222,6 +226,7 @@
         DBVar('restart_state', ty='str'),
         DBVar('restart_time',  ty='float'),
         DBVar('restart_count', ty='int'),
+        DBVar('target',        ty='long', path="memory/target"),
         ]
     
     def __init__(self, db):
@@ -239,6 +244,8 @@
         self.memory = None
         self.ssidref = None
         self.image = None
+
+        self.target = None
 
         self.channel = None
         self.store_channel = None
@@ -315,6 +322,7 @@
         self.info = info
         self.memory = self.info['mem_kb'] / 1024
         self.ssidref = self.info['ssidref']
+        self.target = self.info['mem_kb'] * 1024
 
     def state_set(self, state):
         self.state_updated.acquire()
@@ -399,7 +407,8 @@
                 ['id', self.id],
                 ['name', self.name],
                 ['memory', self.memory],
-                ['ssidref', self.ssidref] ]
+                ['ssidref', self.ssidref],
+                ['target', self.target] ]
         if self.uuid:
             sxpr.append(['uuid', self.uuid])
         if self.info:
@@ -536,6 +545,7 @@
         self.memory = int(sxp.child_value(config, 'memory'))
         if self.memory is None:
             raise VmError('missing memory size')
+        self.target = self.memory * (1 << 20)
         self.ssidref = int(sxp.child_value(config, 'ssidref'))
         cpu = sxp.child_value(config, 'cpu')
         if self.recreate and self.id and cpu is not None and int(cpu) >= 0:
@@ -947,11 +957,12 @@
             index[field_name] = field_index + 1
 
     def mem_target_set(self, target):
-        """Set domain memory target in pages.
-        """
-        if self.channel:
-            msg = messages.packMsg('mem_request_t', { 'target' : target * (1 << 8)} )
-            self.channel.writeRequest(msg)
+        """Set domain memory target in bytes.
+        """
+        if target:
+            self.target = target * (1 << 20)
+            # Commit to XenStore immediately
+            self.exportToDB()
 
     def vcpu_hotplug(self, vcpu, state):
         """Disable or enable VCPU in domain.

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-- 
Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms@us.ibm.com

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