xen: find unused contiguous memory area

For being able to relocate pre-allocated data areas like initrd or
p2m list it is mandatory to find a contiguous memory area which is
not yet in use and doesn't conflict with the memory map we want to
be in effect.

In case such an area is found reserve it at once as this will be
required to be done in any case.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 99ef82cc4edc3bd8c6e2b2674b0ce1c565998398..973d29441f965025be794e0f0650940be7422b58 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>

diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index a4cbb76642d8746eb8dd7a35e2f18a305ff0ee86..c4c3c23597a56079846e42468b93af65bab5a885 100644 (file)
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -43,6 +43,7 @@ bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size);
 unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
 void __init xen_inv_extra_mem(void);
 void __init xen_remap_memory(void);
+phys_addr_t __init xen_find_free_area(phys_addr_t size);
 char * __init xen_memory_setup(void);
 char * xen_auto_xlated_memory_setup(void);
 void __init xen_arch_setup(void);