From 66946f676776a6ef333db1cf7453ecf8a66c90df Mon Sep 17 00:00:00 2001
From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Date: Tue, 14 Sep 2010 10:32:32 -0700
Subject: 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>

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 77b5dc3..2b17ad5 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
-- 
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