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Subject[PATCH 04/40] xen: document Xen is using an unused bit for the pagetables
Date
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@redhat.com>
---
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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