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-rw-r--r--arch/x86_64/kernel/e820.c34
1 files changed, 34 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
index 6ded3a50dfe..b548dea4e5b 100644
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -185,6 +185,40 @@ unsigned long __init e820_end_of_ram(void)
}
/*
+ * Compute how much memory is missing in a range.
+ * Unlike the other functions in this file the arguments are in page numbers.
+ */
+unsigned long __init
+e820_hole_size(unsigned long start_pfn, unsigned long end_pfn)
+{
+ unsigned long ram = 0;
+ unsigned long start = start_pfn << PAGE_SHIFT;
+ unsigned long end = end_pfn << PAGE_SHIFT;
+ int i;
+ for (i = 0; i < e820.nr_map; i++) {
+ struct e820entry *ei = &e820.map[i];
+ unsigned long last, addr;
+
+ if (ei->type != E820_RAM ||
+ ei->addr+ei->size <= start ||
+ ei->addr >= end)
+ continue;
+
+ addr = round_up(ei->addr, PAGE_SIZE);
+ if (addr < start)
+ addr = start;
+
+ last = round_down(ei->addr + ei->size, PAGE_SIZE);
+ if (last >= end)
+ last = end;
+
+ if (last > addr)
+ ram += last - addr;
+ }
+ return ((end - start) - ram) >> PAGE_SHIFT;
+}
+
+/*
* Mark e820 reserved areas as busy for the resource manager.
*/
void __init e820_reserve_resources(void)