On Mon, Aug 31, 2015 at 03:10:39PM +0100, Chris Wilson wrote: > There have been many hard to track down bugs whereby userspace forgot to > flag a write buffer and then cause graphics corruption or a hung GPU > when that buffer was later purged under memory pressure (as the buffer > appeared clean, its pages would have been evicted rather than preserved > and any changes more recent than in the backing storage would be lost). > In retrospect this is a rare optimisation against memory pressure, > already the slow path. If we always mark the buffer as dirty when > accessed by the GPU, anything not used can still be evicted cheaply > (ideal behaviour for mark-and-sweep eviction) but we do not run the risk > of corruption. For correct read serialisation, userspace still has to > notify when the GPU writes to an object. However, there are certain > situations under which userspace may wish to tell white lies to the > kernel... > > Signed-off-by: Chris Wilson <[email protected]> > Cc: Daniel Vetter <[email protected]> > Cc: Kristian Høgsberg <[email protected]> > Cc: Jesse Barnes <[email protected]> > Cc: "Goel, Akash" <[email protected]> > Cc: Michał Winiarski <[email protected]> > Cc: [email protected]
Reviewed-by: Daniel Vetter <[email protected]> > --- > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > index 923a3c4bf0b7..a953d4975b8c 100644 > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c > @@ -1032,6 +1032,7 @@ i915_gem_execbuffer_move_to_active(struct list_head > *vmas, > u32 old_read = obj->base.read_domains; > u32 old_write = obj->base.write_domain; > > + obj->dirty = 1; /* be paranoid */ > obj->base.write_domain = obj->base.pending_write_domain; > if (obj->base.write_domain == 0) > obj->base.pending_read_domains |= > obj->base.read_domains; > @@ -1039,7 +1040,6 @@ i915_gem_execbuffer_move_to_active(struct list_head > *vmas, > > i915_vma_move_to_active(vma, req); > if (obj->base.write_domain) { > - obj->dirty = 1; > i915_gem_request_assign(&obj->last_write_req, req); > > intel_fb_obj_invalidate(obj, ORIGIN_CS); > -- > 2.5.1 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
