xen/balloon: simplify test for the end of usable RAM

When initializing the balloon only max_pfn needs to be checked
(max_pfn will always be <= e820_end_of_ram_pfn()) and improve the
confusing comment.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 9 insertions, 9 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 4f59fb373381..9efb993090aa 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -586,16 +586,16 @@ static int __init balloon_init(void)
 #endif
 
         /*
-         * Initialise the balloon with excess memory space.  We need
-         * to make sure we don't add memory which doesn't exist or
-         * logically exist.  The E820 map can be trimmed to be smaller
-         * than the amount of physical memory due to the mem= command
-         * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
-         * on a system with memory which requires highmem to access,
-         * don't try to use it.
+         * Initialize the balloon with pages from the extra memory
+         * region (see arch/x86/xen/setup.c).
+         *
+         * If the amount of usable memory has been limited (e.g., with
+         * the 'mem' command line parameter), don't add pages beyond
+         * this limit.
          */
-        extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
-                            (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
+        extra_pfn_end = min(max_pfn,
+                            (unsigned long)PFN_DOWN(xen_extra_mem_start
+                                                    + xen_extra_mem_size));
         for (pfn = PFN_UP(xen_extra_mem_start);
              pfn < extra_pfn_end;
              pfn++) {