1 files changed, 36 insertions, 2 deletions

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 328b00305426..dd2eb2a9303f 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -19,6 +19,7 @@
 
 #include <xen/page.h>
 #include <xen/interface/callback.h>
+#include <xen/interface/memory.h>
 #include <xen/interface/physdev.h>
 #include <xen/interface/memory.h>
 #include <xen/features.h>
@@ -107,13 +108,46 @@ static unsigned long __init xen_return_unused_memory(unsigned long max_pfn,
 
 char * __init xen_memory_setup(void)
 {
+        static struct e820entry map[E820MAX] __initdata;
+
         unsigned long max_pfn = xen_start_info->nr_pages;
+        unsigned long long mem_end;
+        int rc;
+        struct xen_memory_map memmap;
+        int i;
 
         max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
+        mem_end = PFN_PHYS(max_pfn);
+
+        memmap.nr_entries = E820MAX;
+        set_xen_guest_handle(memmap.buffer, map);
+
+        rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+        if (rc == -ENOSYS) {
+                memmap.nr_entries = 1;
+                map[0].addr = 0ULL;
+                map[0].size = mem_end;
+                /* 8MB slack (to balance backend allocations). */
+                map[0].size += 8ULL << 20;
+                map[0].type = E820_RAM;
+                rc = 0;
+        }
+        BUG_ON(rc);
 
         e820.nr_map = 0;
-
-        e820_add_region(0, PFN_PHYS((u64)max_pfn), E820_RAM);
+        for (i = 0; i < memmap.nr_entries; i++) {
+                unsigned long long end = map[i].addr + map[i].size;
+                if (map[i].type == E820_RAM) {
+                        if (map[i].addr > mem_end)
+                                continue;
+                        if (end > mem_end) {
+                                /* Truncate region to max_mem. */
+                                map[i].size -= end - mem_end;
+                        }
+                }
+                if (map[i].size > 0)
+                        e820_add_region(map[i].addr, map[i].size, map[i].type);
+        }
 
         /*
          * Even though this is normal, usable memory under Xen, reserve