3 files changed, 48 insertions, 5 deletions

diff --git a/arch/x86/include/asm/iomap.h b/arch/x86/include/asm/iomap.h
index 86af26091d6..bd46495ff7d 100644
--- a/arch/x86/include/asm/iomap.h
+++ b/arch/x86/include/asm/iomap.h
@@ -24,7 +24,10 @@
 #include <asm/tlbflush.h>
 
 int
-is_io_mapping_possible(resource_size_t base, unsigned long size);
+reserve_io_memtype_wc(u64 base, unsigned long size, pgprot_t *prot);
+
+void
+free_io_memtype(u64 base, unsigned long size);
 
 void *
 iomap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot);
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 6c2b1af1692..94596f794b1 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -21,13 +21,13 @@
 #include <linux/module.h>
 
 #ifdef CONFIG_X86_PAE
-int
+static int
 is_io_mapping_possible(resource_size_t base, unsigned long size)
 {
 	return 1;
 }
 #else
-int
+static int
 is_io_mapping_possible(resource_size_t base, unsigned long size)
 {
 	/* There is no way to map greater than 1 << 32 address without PAE */
@@ -38,6 +38,44 @@ is_io_mapping_possible(resource_size_t base, unsigned long size)
 }
 #endif
 
+int
+reserve_io_memtype_wc(u64 base, unsigned long size, pgprot_t *prot)
+{
+	unsigned long ret_flag;
+
+	if (!is_io_mapping_possible(base, size))
+		goto out_err;
+
+	if (!pat_enabled) {
+		*prot = pgprot_noncached(PAGE_KERNEL);
+		return 0;
+	}
+
+	if (reserve_memtype(base, base + size, _PAGE_CACHE_WC, &ret_flag))
+		goto out_err;
+
+	if (ret_flag == _PAGE_CACHE_WB)
+		goto out_free;
+
+	if (kernel_map_sync_memtype(base, size, ret_flag))
+		goto out_free;
+
+	*prot = __pgprot(__PAGE_KERNEL | ret_flag);
+	return 0;
+
+out_free:
+	free_memtype(base, base + size);
+out_err:
+	return -EINVAL;
+}
+
+void
+free_io_memtype(u64 base, unsigned long size)
+{
+	if (pat_enabled)
+		free_memtype(base, base + size);
+}
+
 /* Map 'pfn' using fixed map 'type' and protections 'prot'
  */
 void *
diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
index cbc2f0cd631..f1ed66c4378 100644
--- a/include/linux/io-mapping.h
+++ b/include/linux/io-mapping.h
@@ -49,8 +49,9 @@ static inline struct io_mapping *
 io_mapping_create_wc(resource_size_t base, unsigned long size)
 {
 	struct io_mapping *iomap;
+	pgprot_t prot;
 
-	if (!is_io_mapping_possible(base, size))
+	if (!reserve_io_memtype_wc(base, size, &prot))
 		return NULL;
 
 	iomap = kmalloc(sizeof(*iomap), GFP_KERNEL);
@@ -59,13 +60,14 @@ io_mapping_create_wc(resource_size_t base, unsigned long size)
 
 	iomap->base = base;
 	iomap->size = size;
-	iomap->prot = pgprot_writecombine(__pgprot(__PAGE_KERNEL));
+	iomap->prot = prot;
 	return iomap;
 }
 
 static inline void
 io_mapping_free(struct io_mapping *mapping)
 {
+	free_io_memtype(mapping->base, mapping->size);
 	kfree(mapping);
 }