Commit daf2baff authored by Chris Wilson's avatar Chris Wilson Committed by Luis Henriques

drm/i915: Always mark the object as dirty when used by the GPU

commit 51bc1404 upstream.

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: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Kristian Høgsberg <krh@bitplanet.net>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: "Goel, Akash" <akash.goel@intel.co>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 6bc4db5f
......@@ -965,6 +965,7 @@ 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;
......@@ -973,7 +974,6 @@ i915_gem_execbuffer_move_to_active(struct list_head *vmas,
i915_vma_move_to_active(vma, ring);
if (obj->base.write_domain) {
obj->dirty = 1;
obj->last_write_seqno = intel_ring_get_seqno(ring);
/* check for potential scanout */
if (i915_gem_obj_ggtt_bound(obj) &&
......
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