[RFC PATCH 2/11] x86, mm, pat: Define _PAGE_CACHE_WT for PA3/7 of PAT

[Toshi Kani]

This patch defines _PAGE_CACHE_WT and its relevant macros, which
now use the PA3/7 slot in the PAT MSR.  pat_init() is also changed
to set the WT memory type to the PA3/7 slot in the PAT MSR.

Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
---
 arch/x86/include/asm/pgtable_types.h |    5 +++++
 arch/x86/mm/pat.c                    |    8 ++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 03d40da..7b905cb 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -132,6 +132,7 @@
 #define _PAGE_CACHE_MASK	(_PAGE_PCD | _PAGE_PWT)
 #define _PAGE_CACHE_WB		(0)
 #define _PAGE_CACHE_WC		(_PAGE_PWT)
+#define _PAGE_CACHE_WT		(_PAGE_PCD | _PAGE_PWT)
 #define _PAGE_CACHE_UC_MINUS	(_PAGE_PCD)
 #define _PAGE_CACHE_UC		(_PAGE_CACHE_UC_MINUS)
 
@@ -159,6 +160,7 @@
 #define __PAGE_KERNEL_RX		(__PAGE_KERNEL_EXEC & ~_PAGE_RW)
 #define __PAGE_KERNEL_EXEC_NOCACHE	(__PAGE_KERNEL_EXEC | _PAGE_CACHE_UC)
 #define __PAGE_KERNEL_WC		(__PAGE_KERNEL | _PAGE_CACHE_WC)
+#define __PAGE_KERNEL_WT		(__PAGE_KERNEL | _PAGE_CACHE_WT)
 #define __PAGE_KERNEL_NOCACHE		(__PAGE_KERNEL | _PAGE_CACHE_UC)
 #define __PAGE_KERNEL_UC_MINUS		(__PAGE_KERNEL | _PAGE_CACHE_UC_MINUS)
 #define __PAGE_KERNEL_VSYSCALL		(__PAGE_KERNEL_RX | _PAGE_USER)
@@ -172,12 +174,14 @@
 #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_IO_WT		(__PAGE_KERNEL_WT | _PAGE_IOMAP)
 
 #define PAGE_KERNEL			__pgprot(__PAGE_KERNEL)
 #define PAGE_KERNEL_RO			__pgprot(__PAGE_KERNEL_RO)
 #define PAGE_KERNEL_EXEC		__pgprot(__PAGE_KERNEL_EXEC)
 #define PAGE_KERNEL_RX			__pgprot(__PAGE_KERNEL_RX)
 #define PAGE_KERNEL_WC			__pgprot(__PAGE_KERNEL_WC)
+#define PAGE_KERNEL_WT			__pgprot(__PAGE_KERNEL_WT)
 #define PAGE_KERNEL_NOCACHE		__pgprot(__PAGE_KERNEL_NOCACHE)
 #define PAGE_KERNEL_UC_MINUS		__pgprot(__PAGE_KERNEL_UC_MINUS)
 #define PAGE_KERNEL_EXEC_NOCACHE	__pgprot(__PAGE_KERNEL_EXEC_NOCACHE)
@@ -192,6 +196,7 @@
 #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)
+#define PAGE_KERNEL_IO_WT		__pgprot(__PAGE_KERNEL_IO_WT)
 
 /*         xwr */
 #define __P000	PAGE_NONE
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index c3567a5..176d4d6 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -101,7 +101,7 @@ void pat_init(void)
 		}
 	}
 
-	/* Set PWT to Write-Combining. All other bits stay the same */
+	/* Set PWT to Write-Combining, and PCD|PWT to Write-Through. */
 	/*
 	 * PTE encoding used in Linux:
 	 *      PAT
@@ -111,11 +111,11 @@ void pat_init(void)
 	 *      000 WB		_PAGE_CACHE_WB
 	 *      001 WC		_PAGE_CACHE_WC
 	 *      010 UC-		_PAGE_CACHE_UC_MINUS
-	 *      011 UC		_PAGE_CACHE_UC
+	 *      011 WT		_PAGE_CACHE_WT
 	 * PAT bit unused
 	 */
-	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
-	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+	pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, WT) |
+	      PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, WT);
 
 	/* Boot CPU check */
 	if (!boot_pat_state)
--
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