x86, pat: New i/f for driver to request memtype for IO regions

Add new routines to request memtype for IO regions. This will currently
be a backend for io_mapping_* routines. But, it can also be made available
to drivers directly in future, in case it is needed.

reserve interface reserves the memory, makes sure we have a compatible
memory type available and keeps the identity map in sync when needed.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 54 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 7af14e512f97..e2c1668dde7a 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -19,4 +19,9 @@ extern int free_memtype(u64 start, u64 end);
 extern int kernel_map_sync_memtype(u64 base, unsigned long size,
                 unsigned long flag);
 
+int io_reserve_memtype(resource_size_t start, resource_size_t end,
+                        unsigned long *type);
+
+void io_free_memtype(resource_size_t start, resource_size_t end);
+
 #endif /* _ASM_X86_PAT_H */
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index d5af2792d2fd..82d097ce3091 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -498,6 +498,55 @@ int free_memtype(u64 start, u64 end)
 }
 
 
+/**
+ * io_reserve_memtype - Request a memory type mapping for a region of memory
+ * @start: start (physical address) of the region
+ * @end: end (physical address) of the region
+ * @type: A pointer to memtype, with requested type. On success, requested
+ * or any other compatible type that was available for the region is returned
+ *
+ * On success, returns 0
+ * On failure, returns non-zero
+ */
+int io_reserve_memtype(resource_size_t start, resource_size_t end,
+                        unsigned long *type)
+{
+        unsigned long req_type = *type;
+        unsigned long new_type;
+        int ret;
+
+        WARN_ON_ONCE(iomem_map_sanity_check(start, end - start));
+
+        ret = reserve_memtype(start, end, req_type, &new_type);
+        if (ret)
+                goto out_err;
+
+        if (!is_new_memtype_allowed(req_type, new_type))
+                goto out_free;
+
+        if (kernel_map_sync_memtype(start, end - start, new_type) < 0)
+                goto out_free;
+
+        *type = new_type;
+        return 0;
+
+out_free:
+        free_memtype(start, end);
+        ret = -EBUSY;
+out_err:
+        return ret;
+}
+
+/**
+ * io_free_memtype - Release a memory type mapping for a region of memory
+ * @start: start (physical address) of the region
+ * @end: end (physical address) of the region
+ */
+void io_free_memtype(resource_size_t start, resource_size_t end)
+{
+        free_memtype(start, end);
+}
+
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                                 unsigned long size, pgprot_t vma_prot)
 {