| Message ID | 20190404101914.7231-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/i915: Be precise in types for i915_gem_busy | expand |
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@chris-wilson.co.uk> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > --- > 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@intel.com> Regards, Tvrtko
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); }
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@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> --- 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(-)