| Message ID | 20210518082701.997251-7-thomas.hellstrom@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Move LMEM (VRAM) management over to TTM | expand |
Op 18-05-2021 om 10:26 schreef Thomas Hellström: > Embed a struct ttm_buffer_object into the i915 gem object, making sure > we alias the gem object part. It's a bit unfortunate that the > struct ttm_buffer_ojbect embeds a gem object since we otherwise could > make the TTM part private to the TTM backend, and use the usual > i915 gem object for the other backends. > To make this a bit more storage efficient for the other backends, > we'd have to use a pointer for the gem object which would require > a lot of changes in the driver. We postpone that for later. > > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > --- > drivers/gpu/drm/i915/gem/i915_gem_object.c | 7 +++++++ > drivers/gpu/drm/i915/gem/i915_gem_object_types.h | 12 +++++++++++- > 2 files changed, 18 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 abadf0994ad0..c8953e3f5c70 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c > @@ -62,6 +62,13 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj, > const struct drm_i915_gem_object_ops *ops, > struct lock_class_key *key, unsigned flags) > { > + /* > + * A gem object is embedded both in a struct ttm_buffer_object :/ and > + * in a drm_i915_gem_object. Make sure they are aliased. > + */ > + BUILD_BUG_ON(offsetof(typeof(*obj), base) != > + offsetof(typeof(*obj), __do_not_access.base)); > + > spin_lock_init(&obj->vma.lock); > INIT_LIST_HEAD(&obj->vma.list); > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h > index dbd7fffe956e..98f69d8fd37d 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h > @@ -10,6 +10,7 @@ > #include <linux/mmu_notifier.h> > > #include <drm/drm_gem.h> > +#include <drm/ttm/ttm_bo_api.h> > #include <uapi/drm/i915_drm.h> > > #include "i915_active.h" > @@ -99,7 +100,16 @@ struct i915_gem_object_page_iter { > }; > > struct drm_i915_gem_object { > - struct drm_gem_object base; > + /* > + * We might have reason to revisit the below since it wastes > + * a lot of space for non-ttm gem objects. > + * In any case, always use the accessors for the ttm_buffer_object > + * when accessing it. > + */ > + union { > + struct drm_gem_object base; > + struct ttm_buffer_object __do_not_access; > + }; > > const struct drm_i915_gem_object_ops *ops; > Considering Dave did roughly the same in his patches, I don't think there's a better way to do this. Although he just wrapped base.base using sizes. This works too. It probably needs someone else's r-b too, to ensure this is allowed. Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c index abadf0994ad0..c8953e3f5c70 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c @@ -62,6 +62,13 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj, const struct drm_i915_gem_object_ops *ops, struct lock_class_key *key, unsigned flags) { + /* + * A gem object is embedded both in a struct ttm_buffer_object :/ and + * in a drm_i915_gem_object. Make sure they are aliased. + */ + BUILD_BUG_ON(offsetof(typeof(*obj), base) != + offsetof(typeof(*obj), __do_not_access.base)); + spin_lock_init(&obj->vma.lock); INIT_LIST_HEAD(&obj->vma.list); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h index dbd7fffe956e..98f69d8fd37d 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h @@ -10,6 +10,7 @@ #include <linux/mmu_notifier.h> #include <drm/drm_gem.h> +#include <drm/ttm/ttm_bo_api.h> #include <uapi/drm/i915_drm.h> #include "i915_active.h" @@ -99,7 +100,16 @@ struct i915_gem_object_page_iter { }; struct drm_i915_gem_object { - struct drm_gem_object base; + /* + * We might have reason to revisit the below since it wastes + * a lot of space for non-ttm gem objects. + * In any case, always use the accessors for the ttm_buffer_object + * when accessing it. + */ + union { + struct drm_gem_object base; + struct ttm_buffer_object __do_not_access; + }; const struct drm_i915_gem_object_ops *ops;
Embed a struct ttm_buffer_object into the i915 gem object, making sure we alias the gem object part. It's a bit unfortunate that the struct ttm_buffer_ojbect embeds a gem object since we otherwise could make the TTM part private to the TTM backend, and use the usual i915 gem object for the other backends. To make this a bit more storage efficient for the other backends, we'd have to use a pointer for the gem object which would require a lot of changes in the driver. We postpone that for later. Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> --- drivers/gpu/drm/i915/gem/i915_gem_object.c | 7 +++++++ drivers/gpu/drm/i915/gem/i915_gem_object_types.h | 12 +++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-)