x86, fixmap: define reserve_top_address for x86_64

Impact: new interface (not yet use)

Define reserve_top_address for x86_64; only for later x86 integration.

Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Acked-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 86f2ffc..5b7c7c84 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -313,6 +313,24 @@ int ptep_clear_flush_young(struct vm_area_struct *vma,
 	return young;
 }
 
+/**
+ * reserve_top_address - reserves a hole in the top of kernel address space
+ * @reserve - size of hole to reserve
+ *
+ * Can be used to relocate the fixmap area and poke a hole in the top
+ * of kernel address space to make room for a hypervisor.
+ */
+void __init reserve_top_address(unsigned long reserve)
+{
+#ifdef CONFIG_X86_32
+	BUG_ON(fixmaps_set > 0);
+	printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
+	       (int)-reserve);
+	__FIXADDR_TOP = -reserve - PAGE_SIZE;
+	__VMALLOC_RESERVE += reserve;
+#endif
+}
+
 int fixmaps_set;
 
 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)