[PATCH v4 4/7] x86, mm, pat: Add pgprot_writethrough() for WT

[Toshi Kani <toshi.kani@hp.com>]

This patch adds pgprot_writethrough() for setting WT to a given
pgprot_t.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/include/asm/pgtable_types.h |    3 +++
 arch/x86/mm/pat.c                    |   10 ++++++++++
 include/asm-generic/pgtable.h        |    4 ++++
 3 files changed, 17 insertions(+)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 31c66c6..eebf2a1 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -407,6 +407,9 @@ extern int nx_enabled;
 #define pgprot_writecombine	pgprot_writecombine
 extern pgprot_t pgprot_writecombine(pgprot_t prot);
 
+#define pgprot_writethrough	pgprot_writethrough
+extern pgprot_t pgprot_writethrough(pgprot_t prot);
+
 /* Indicate that x86 has its own track and untrack pfn vma functions */
 #define __HAVE_PFNMAP_TRACKING
 
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index a214f5a..a0264d3 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -896,6 +896,16 @@ pgprot_t pgprot_writecombine(pgprot_t prot)
 }
 EXPORT_SYMBOL_GPL(pgprot_writecombine);
 
+pgprot_t pgprot_writethrough(pgprot_t prot)
+{
+	if (pat_enabled)
+		return __pgprot(pgprot_val(prot) |
+				cachemode2protval(_PAGE_CACHE_MODE_WT));
+	else
+		return pgprot_noncached(prot);
+}
+EXPORT_SYMBOL_GPL(pgprot_writethrough);
+
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
 
 static struct memtype *memtype_get_idx(loff_t pos)
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 752e30d..9ad756e 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -249,6 +249,10 @@ static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 #define pgprot_writecombine pgprot_noncached
 #endif
 
+#ifndef pgprot_writethrough
+#define pgprot_writethrough pgprot_noncached
+#endif
+
 #ifndef pgprot_device
 #define pgprot_device pgprot_noncached
 #endif

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