xen: find unused contiguous memory area

[cascardo/linux.git] / arch / x86 / xen / setup.c

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 99ef82c..973d294 100644 (file)
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -596,6 +596,40 @@ bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
        return true;
 }
 
+/*
+ * Find a free area in physical memory not yet reserved and compliant with
+ * E820 map.
+ * Used to relocate pre-allocated areas like initrd or p2m list which are in
+ * conflict with the to be used E820 map.
+ * In case no area is found, return 0. Otherwise return the physical address
+ * of the area which is already reserved for convenience.
+ */
+phys_addr_t __init xen_find_free_area(phys_addr_t size)
+{
+       unsigned mapcnt;
+       phys_addr_t addr, start;
+       struct e820entry *entry = xen_e820_map;
+
+       for (mapcnt = 0; mapcnt < xen_e820_map_entries; mapcnt++, entry++) {
+               if (entry->type != E820_RAM || entry->size < size)
+                       continue;
+               start = entry->addr;
+               for (addr = start; addr < start + size; addr += PAGE_SIZE) {
+                       if (!memblock_is_reserved(addr))
+                               continue;
+                       start = addr + PAGE_SIZE;
+                       if (start + size > entry->addr + entry->size)
+                               break;
+               }
+               if (addr >= start + size) {
+                       memblock_reserve(start, size);
+                       return start;
+               }
+       }
+
+       return 0;
+}
+
 /*
  * Reserve Xen mfn_list.
  * See comment above "struct start_info" in <xen/interface/xen.h>