[Xen-devel] [PATCH 8/9] mini-os: get maximum memory size from hypervisor

[Juergen Gross <jgross@xxxxxxxx>]

Add support for obtaining the maximum memory size from the hypervisor.
This will make it possible to support ballooning.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 include/mm.h |  1 +
 mm.c         | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/mm.h b/include/mm.h
index b97b43e..161483f 100644
--- a/include/mm.h
+++ b/include/mm.h
@@ -43,6 +43,7 @@
 #define STACK_SIZE __STACK_SIZE
 
 extern unsigned long nr_free_pages;
+extern unsigned long nr_max_pages;
 
 void init_mm(void);
 unsigned long alloc_pages(int order);
diff --git a/mm.c b/mm.c
index 185a8a5..d4a8f1e 100644
--- a/mm.c
+++ b/mm.c
@@ -54,6 +54,7 @@ static unsigned long *alloc_bitmap;
 (alloc_bitmap[(_pn)/PAGES_PER_MAPWORD] & (1UL<<((_pn)&(PAGES_PER_MAPWORD-1))))
 
 unsigned long nr_free_pages;
+unsigned long nr_max_pages;
 
 /*
  * Hint regarding bitwise arithmetic in map_{alloc,free}:
@@ -350,7 +351,27 @@ void *sbrk(ptrdiff_t increment)
 }
 #endif
 
+#ifdef CONFIG_BALLOON
+static void get_max_pages(void)
+{
+    long ret;
+    domid_t domid = DOMID_SELF;
 
+    ret = HYPERVISOR_memory_op(XENMEM_maximum_reservation, &domid);
+    if (ret < 0) {
+        printk("Could not get maximum pfn\n");
+        return;
+    }
+
+    nr_max_pages = ret;
+    printk("Maximum memory size: %ld pages\n", nr_max_pages);
+}
+#else
+static unsigned long get_max_pages(void)
+{
+    return 0;
+}
+#endif
 
 void init_mm(void)
 {
@@ -359,6 +380,7 @@ void init_mm(void)
 
     printk("MM: Init\n");
 
+    get_max_pages();
     arch_init_mm(&start_pfn, &max_pfn);
     /*
      * now we can initialise the page allocator
-- 
2.6.6


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