On 19/02/2018 18:35, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2018-02-19 18:31:31)
On 19/02/2018 14:01, Chris Wilson wrote:
If we fail to unbind the vma (due to a signal on an active buffer that
needs to be moved for the next execbuf), then we need to clear the
persistent tracking state we setup for this execbuf.
Fixes: c7c6e46f913b ("drm/i915: Convert execbuf to use struct-of-array packing for critical fields")
Testcase: igt/gem_fenced_exec_thrash/no-spare-fences-busy*
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 51f3c32c64bf..4eb28e84fda4 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -505,6 +505,8 @@ eb_add_vma(struct i915_execbuffer *eb, unsigned int i, struct i915_vma *vma)
list_add_tail(&vma->exec_link, &eb->unbound);
if (drm_mm_node_allocated(&vma->node))
err = i915_vma_unbind(vma);
+ if (unlikely(err))
+ vma->exec_flags = NULL;
}
return err;
}
I was trying to track down what actually explodes for like 15 minutes.
My track was:
eb_relocate -> eb_lookup_vmas fails -> eb_relocate -> eb_relocate_slow
-> eb_reset_vmas -> second pass to eb_lookup_vmas -> resets
vma->exec_flags. So no explosion.
So in other words I've failed to find what goes wrong and under which
circumstances.
The first eb_relocate calls eb_lookup_vma triggers the failure and exit
from execbuf. In that path, we mark the current index as the sentinel
(err_vma: eb->vma[i] = NULL) which means we do not clear the last vma
when unwinding in eb_release_vmas. So the vma->exec_flags was carried
over into the next execbuf call from userspace.
Ah yes, I missed the !vma continue bit in eb_release vmas.
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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