On 04/04/2019 11:19, Chris Wilson wrote:
Mixing u8 and -1u together leads to zero-extended integer expansion, and
comparing 0x000000ff against 0xffffffff, causing us to report a mixed
uabi-class request as not busy.
The input flag is a u8, and we want to generate a u32 uABI response,
mark our functions so.
Fixes: c8b502422bfe ("drm/i915: Remove last traces of exec-id (GEM_BUSY)")
Testcase: igt/gem_exec_balance/busy
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
Include a typecheck so we notice if we ever change engine->uabi_class.
---
drivers/gpu/drm/i915/i915_gem.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index bf594a5e88bc..f25a1ba24927 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3841,16 +3841,16 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
return vma;
}
-static __always_inline unsigned int __busy_read_flag(unsigned int id)
+static __always_inline u32 __busy_read_flag(u8 id)
{
- if (id == I915_ENGINE_CLASS_INVALID)
- return 0xffff0000;
+ if (id == (u8)I915_ENGINE_CLASS_INVALID)
+ return 0xffff0000u;
GEM_BUG_ON(id >= 16);
- return 0x10000 << id;
+ return 0x10000u << id;
}
-static __always_inline unsigned int __busy_write_id(unsigned int id)
+static __always_inline u32 __busy_write_id(u8 id)
{
/*
* The uABI guarantees an active writer is also amongst the read
@@ -3861,15 +3861,14 @@ static __always_inline unsigned int __busy_write_id(unsigned int id)
* last_read - hence we always set both read and write busy for
* last_write.
*/
- if (id == I915_ENGINE_CLASS_INVALID)
- return 0xffffffff;
+ if (id == (u8)I915_ENGINE_CLASS_INVALID)
+ return 0xffffffffu;
return (id + 1) | __busy_read_flag(id);
}
static __always_inline unsigned int
-__busy_set_if_active(const struct dma_fence *fence,
- unsigned int (*flag)(unsigned int id))
+__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id))
{
const struct i915_request *rq;
@@ -3889,6 +3888,8 @@ __busy_set_if_active(const struct dma_fence *fence,
if (i915_request_completed(rq))
return 0;
+ /* Beware type-expansion follies! */
+ BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class));
return flag(rq->engine->uabi_class);
}
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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