xen/balloon: make sure we only include remaining extra ram

If the user specifies mem= on the kernel command line, some or all
of the extra memory E820 region may be clipped away, so make sure
we don't try to add more extra memory than exists in E820.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 77b5dc3597e3..2b17ad5b4b32 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -50,6 +50,7 @@
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 #include <asm/tlb.h>
+#include <asm/e820.h>
 
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
@@ -391,7 +392,7 @@ static struct notifier_block xenstore_notifier;
 
 static int __init balloon_init(void)
 {
-        unsigned long pfn;
+        unsigned long pfn, extra_pfn_end;
         struct page *page;
 
         if (!xen_pv_domain())
@@ -412,8 +413,10 @@ static int __init balloon_init(void)
         register_balloon(&balloon_sysdev);
 
         /* Initialise the balloon with excess memory space. */
+        extra_pfn_end = min(e820_end_of_ram_pfn(),
+                            (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
         for (pfn = PFN_UP(xen_extra_mem_start);
-             pfn < PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size);
+             pfn < extra_pfn_end;
              pfn++) {
                 page = pfn_to_page(pfn);
                 /* totalram_pages doesn't include the boot-time