drm/radeon: add userptr flag to limit it to anonymous memory v2

Avoid problems with writeback by limiting userptr to anonymous memory.

v2: add commit and code comments

Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_gem.c

@@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data,
 		return -EACCES;
 
 	/* reject unknown flag values */
-	if (args->flags & ~RADEON_GEM_USERPTR_READONLY)
+	if (args->flags & ~(RADEON_GEM_USERPTR_READONLY |
+	    RADEON_GEM_USERPTR_ANONONLY))
 		return -EINVAL;
 
 	/* readonly pages not tested on older hardware */

drivers/gpu/drm/radeon/radeon_ttm.c

@@ -538,6 +538,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm)
 	if (current->mm != gtt->usermm)
 		return -EPERM;
 
+	if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) {
+		/* check that we only pin down anonymous memory
+		   to prevent problems with writeback */
+		unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE;
+		struct vm_area_struct *vma;
+		vma = find_vma(gtt->usermm, gtt->userptr);
+		if (!vma || vma->vm_file || vma->vm_end < end)
+			return -EPERM;
+	}
+
 	do {
 		unsigned num_pages = ttm->num_pages - pinned;
 		uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE;

include/uapi/drm/radeon_drm.h

@@ -816,6 +816,7 @@ struct drm_radeon_gem_create {
  * perform any operation.
  */
 #define RADEON_GEM_USERPTR_READONLY	(1 << 0)
+#define RADEON_GEM_USERPTR_ANONONLY	(1 << 1)
 
 struct drm_radeon_gem_userptr {
 	uint64_t		addr;