[PATCH 03/35] xen: document Xen is using an unused bit for the pagetables

[Andrea Arcangeli]

Xen has taken over the last reserved bit available for the pagetables
which is set through ioremap, this documents it and makes the code
more readable.

Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
---
 arch/x86/include/asm/pgtable_types.h |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 013286a..b74cac9 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -17,7 +17,7 @@
 #define _PAGE_BIT_PAT		7	/* on 4KB pages */
 #define _PAGE_BIT_GLOBAL	8	/* Global TLB entry PPro+ */
 #define _PAGE_BIT_UNUSED1	9	/* available for programmer */
-#define _PAGE_BIT_IOMAP		10	/* flag used to indicate IO mapping */
+#define _PAGE_BIT_UNUSED2	10
 #define _PAGE_BIT_HIDDEN	11	/* hidden by kmemcheck */
 #define _PAGE_BIT_PAT_LARGE	12	/* On 2MB or 1GB pages */
 #define _PAGE_BIT_SPECIAL	_PAGE_BIT_UNUSED1
@@ -41,7 +41,7 @@
 #define _PAGE_PSE	(_AT(pteval_t, 1) << _PAGE_BIT_PSE)
 #define _PAGE_GLOBAL	(_AT(pteval_t, 1) << _PAGE_BIT_GLOBAL)
 #define _PAGE_UNUSED1	(_AT(pteval_t, 1) << _PAGE_BIT_UNUSED1)
-#define _PAGE_IOMAP	(_AT(pteval_t, 1) << _PAGE_BIT_IOMAP)
+#define _PAGE_UNUSED2	(_AT(pteval_t, 1) << _PAGE_BIT_UNUSED2)
 #define _PAGE_PAT	(_AT(pteval_t, 1) << _PAGE_BIT_PAT)
 #define _PAGE_PAT_LARGE (_AT(pteval_t, 1) << _PAGE_BIT_PAT_LARGE)
 #define _PAGE_SPECIAL	(_AT(pteval_t, 1) << _PAGE_BIT_SPECIAL)
@@ -49,6 +49,13 @@
 #define _PAGE_SPLITTING	(_AT(pteval_t, 1) << _PAGE_BIT_SPLITTING)
 #define __HAVE_ARCH_PTE_SPECIAL
 
+/* flag used to indicate IO mapping */
+#ifdef CONFIG_XEN
+#define _PAGE_IOMAP	(_AT(pteval_t, 1) << _PAGE_BIT_UNUSED2)
+#else
+#define _PAGE_IOMAP	(_AT(pteval_t, 0))
+#endif
+
 #ifdef CONFIG_KMEMCHECK
 #define _PAGE_HIDDEN	(_AT(pteval_t, 1) << _PAGE_BIT_HIDDEN)
 #else
--
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