On 22/08/16 09:03, Chris Wilson wrote:
The obj->dirty bit is a companion to the obj->active bits that were
moved to the obj->flags bitmask. Since we also update this bit inside
the i915_vma_move_to_active() hotpath, we can aide gcc by also moving
the obj->dirty bit to obj->flags bitmask.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_debugfs.c | 2 +-
drivers/gpu/drm/i915/i915_drv.h | 22 +++++++++++++++++++++-
drivers/gpu/drm/i915/i915_gem.c | 20 ++++++++++----------
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 3 +--
drivers/gpu/drm/i915/i915_gem_userptr.c | 6 +++---
drivers/gpu/drm/i915/i915_gpu_error.c | 2 +-
drivers/gpu/drm/i915/intel_lrc.c | 6 +++---
7 files changed, 40 insertions(+), 21 deletions(-)
[snip]
@@ -3272,7 +3272,7 @@ i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj, bool write)
if (write) {
obj->base.read_domains = I915_GEM_DOMAIN_GTT;
obj->base.write_domain = I915_GEM_DOMAIN_GTT;
- obj->dirty = 1;
+ i915_gem_object_set_dirty(obj);
At this point the object is or may not be pinned. From our conversation
back in April ...
What I particularly dislike about the current obj->dirty is that it is
strictly only valid inside a pin_pages/unpin_pages section. That isn't
clear from the API atm.
-Chris
So, I tried replacing all instances of "obj->dirty = true" with my
newfunction i915_gem_object_mark_dirty(), and added an assertion that
> it's called only when (pages_pin_count > 0) - and found a failure.
Stack is:
i915_gem_object_mark_dirty
i915_gem_object_set_to_gtt_domain
i915_gem_set_domain_ioctl
So is i915_gem_object_set_to_gtt_domain() wrong? It's done a
get_pages but no pin_pages.
... and the same issue is still there. I think I worked out a
hypothetical scenario where this would lead to data corruption:
* set to GTT => mark dirty
* BO paged out => flushed to swap, marked clean
* BO paged in => still clean
* update contents => still clean?
* get paged out => not written out?
But can this actually happen?
.Dave.
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