[RFC v2 13/26] mm/asi: Add asi_remap() function

[Alexandre Chartre]

Add a function to remap an already mapped buffer with a new address
in an ASI page-table: the already mapped buffer is unmapped, and a
new mapping is added for the specified new address.

This is useful to track and remap a buffer which can be freed and
then reallocated.

Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
---
 arch/x86/include/asm/asi.h  |    1 +
 arch/x86/mm/asi_pagetable.c |   25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index 912b6a7..cf5d198 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -84,6 +84,7 @@ extern int asi_map_range(struct asi *asi, void *ptr, size_t size,
 			 enum page_table_level level);
 extern int asi_map(struct asi *asi, void *ptr, unsigned long size);
 extern void asi_unmap(struct asi *asi, void *ptr);
+extern int asi_remap(struct asi *asi, void **mapping, void *ptr, size_t size);
 
 /*
  * Copy the memory mapping for the current module. This is defined as a
diff --git a/arch/x86/mm/asi_pagetable.c b/arch/x86/mm/asi_pagetable.c
index a4fe867..1ff0c47 100644
--- a/arch/x86/mm/asi_pagetable.c
+++ b/arch/x86/mm/asi_pagetable.c
@@ -842,3 +842,28 @@ int asi_map_percpu(struct asi *asi, void *percpu_ptr, size_t size)
 	return 0;
 }
 EXPORT_SYMBOL(asi_map_percpu);
+
+int asi_remap(struct asi *asi, void **current_ptrp, void *new_ptr, size_t size)
+{
+	void *current_ptr = *current_ptrp;
+	int err;
+
+	if (current_ptr == new_ptr) {
+		/* no change, already mapped */
+		return 0;
+	}
+
+	if (current_ptr) {
+		asi_unmap(asi, current_ptr);
+		*current_ptrp = NULL;
+	}
+
+	err = asi_map(asi, new_ptr, size);
+	if (err)
+		return err;
+
+	*current_ptrp = new_ptr;
+
+	return 0;
+}
+EXPORT_SYMBOL(asi_remap);
-- 
1.7.1