[PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag for IO mappings

Jeremy Fitzhardinge
2008-09-07T22:24:56Z

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>
---
arch/x86/mm/init_32.c | 2 +-
arch/x86/mm/init_64.c | 2 +-
arch/x86/mm/ioremap.c | 8 ++++----
include/asm-x86/fixmap.h | 2 +-
include/asm-x86/pgtable.h | 14 ++++++++++++--
5 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -503,7 +503,7 @@

int nx_enabled;

-pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL);
+pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL | _PAGE_IOMAP);
EXPORT_SYMBOL_GPL(__supported_pte_mask);

#ifdef CONFIG_X86_PAE
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -88,7 +88,7 @@

int after_bootmem;

-unsigned long __supported_pte_mask __read_mostly = ~0UL;
+pteval_t __supported_pte_mask __read_mostly = ~_PAGE_IOMAP;
EXPORT_SYMBOL_GPL(__supported_pte_mask);

static int do_not_nx __cpuinitdata;
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -223,16 +223,16 @@
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;
}

diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -15,7 +15,7 @@
#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_UNUSED2 10
+#define _PAGE_BIT_IOMAP 10 /* flag used to indicate IO mapping */
#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
@@ -32,7 +32,7 @@
#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_UNUSED2 (_AT(pteval_t, 1) << _PAGE_BIT_UNUSED2)
+#define _PAGE_IOMAP (_AT(pteval_t, 1) << _PAGE_BIT_IOMAP)
#define _PAGE_HIDDEN (_AT(pteval_t, 1) << _PAGE_BIT_HIDDEN)
#define _PAGE_PAT (_AT(pteval_t, 1) << _PAGE_BIT_PAT)
#define _PAGE_PAT_LARGE (_AT(pteval_t, 1) << _PAGE_BIT_PAT_LARGE)
@@ -99,6 +99,11 @@
#define __PAGE_KERNEL_LARGE_NOCACHE (__PAGE_KERNEL | _PAGE_CACHE_UC | _PAGE_PSE)
#define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE)

+#define __PAGE_KERNEL_IO (__PAGE_KERNEL | _PAGE_IOMAP)
+#define __PAGE_KERNEL_IO_NOCACHE (__PAGE_KERNEL_NOCACHE | _PAGE_IOMAP)
+#define __PAGE_KERNEL_IO_UC_MINUS (__PAGE_KERNEL_UC_MINUS | _PAGE_IOMAP)
+#define __PAGE_KERNEL_IO_WC (__PAGE_KERNEL_WC | _PAGE_IOMAP)
+
#define PAGE_KERNEL __pgprot(__PAGE_KERNEL)
#define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO)
#define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC)
@@ -112,6 +117,11 @@
#define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC)
#define PAGE_KERNEL_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL)
#define PAGE_KERNEL_VSYSCALL_NOCACHE __pgprot(__PAGE_KERNEL_VSYSCALL_NOCACHE)
+
+#define PAGE_KERNEL_IO __pgprot(__PAGE_KERNEL_IO)
+#define PAGE_KERNEL_IO_NOCACHE __pgprot(__PAGE_KERNEL_IO_NOCACHE)
+#define PAGE_KERNEL_IO_UC_MINUS __pgprot(__PAGE_KERNEL_IO_UC_MINUS)
+#define PAGE_KERNEL_IO_WC __pgprot(__PAGE_KERNEL_IO_WC)

/* xwr */
#define __P000 PAGE_NONE