[Intel-gfx] [PATCH 2/2] drm/i915: check memory is mappable in read_from_page

[Matthew Auld]

On small-bar systems we could be given something non-mappable here,
which leads to nasty oops. Make this nicer by checking if the resource
is mappable or not, and return an error otherwise.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Jianshui Yu <jianshui.yu at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Nirmoy Das <nirmoy.das at intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index 369006c5317f..0a3dbb08376a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -444,6 +444,16 @@ i915_gem_object_read_from_page_iomap(struct drm_i915_gem_object *obj, u64 offset
 	io_mapping_unmap(src_map);
 }
 
+static bool object_has_mappable_iomem(struct drm_i915_gem_object *obj)
+{
+	GEM_BUG_ON(!i915_gem_object_has_iomem(obj));
+
+	if (IS_DGFX(to_i915(obj->base.dev)))
+		return i915_ttm_resource_mappable(i915_gem_to_ttm(obj)->resource);
+
+	return true;
+}
+
 /**
  * i915_gem_object_read_from_page - read data from the page of a GEM object
  * @obj: GEM object to read from
@@ -463,10 +473,11 @@ int i915_gem_object_read_from_page(struct drm_i915_gem_object *obj, u64 offset,
 	GEM_BUG_ON(offset >= obj->base.size);
 	GEM_BUG_ON(offset_in_page(offset) > PAGE_SIZE - size);
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
+	GEM_BUG_ON(obj->flags & I915_BO_ALLOC_GPU_ONLY);
 
 	if (i915_gem_object_has_struct_page(obj))
 		i915_gem_object_read_from_page_kmap(obj, offset, dst, size);
-	else if (i915_gem_object_has_iomem(obj))
+	else if (i915_gem_object_has_iomem(obj) && object_has_mappable_iomem(obj))
 		i915_gem_object_read_from_page_iomap(obj, offset, dst, size);
 	else
 		return -ENODEV;
-- 
2.37.3