x86: add _PAGE_IOMAP pte flag for IO mappings

Use one of the software-defined PTE bits to indicate that a mapping is
intended for an IO address.  On native hardware this is irrelevent,
since a physical address is a physical address.  But in a virtual
environment, physical addresses are also virtualized, so there needs
to be some way to distinguish between pseudo-physical addresses and
actual hardware addresses; _PAGE_IOMAP indicates this intent.

By default, __supported_pte_mask masks out _PAGE_IOMAP, so it doesn't
even appear in the final pagetable.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/ioremap.c

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 8cbeda1..43c3b68 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -242,16 +242,16 @@
 	switch (prot_val) {
 	case _PAGE_CACHE_UC:
 	default:
-		prot = PAGE_KERNEL_NOCACHE;
+		prot = PAGE_KERNEL_IO_NOCACHE;
 		break;
 	case _PAGE_CACHE_UC_MINUS:
-		prot = PAGE_KERNEL_UC_MINUS;
+		prot = PAGE_KERNEL_IO_UC_MINUS;
 		break;
 	case _PAGE_CACHE_WC:
-		prot = PAGE_KERNEL_WC;
+		prot = PAGE_KERNEL_IO_WC;
 		break;
 	case _PAGE_CACHE_WB:
-		prot = PAGE_KERNEL;
+		prot = PAGE_KERNEL_IO;
 		break;
 	}