3 files changed, 48 insertions, 5 deletions

diff --git a/arch/x86/include/asm/iomap.h b/arch/x86/include/asm/iomap.h
index 86af26091d6c..bd46495ff7de 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 6c2b1af16926..94596f794b1b 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 cbc2f0cd631b..f1ed66c43787 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);
 }