| Message ID | 20200115152437.13207-1-tvrtko.ursulin@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Align engine->uabi_class/instance with i915_drm.h | expand |
On 15/01/2020 15:24, Tvrtko Ursulin wrote: > From: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > > In our ABI we have defined I915_ENGINE_CLASS_INVALID_NONE and > I915_ENGINE_CLASS_INVALID_VIRTUAL as negative values which creates > implicit coupling with type widths used in, also ABI, struct > i915_engine_class_instance. > > When for instance we export engine->uabi_class > I915_ENGINE_CLASS_INVALID_VIRTUAL from our our tracepoints, because the > type of the former is u8 in contrast to u16 defined in the ABI, 254 will > be returned instead of 65534 which userspace would legitimately expect. > > Therefore we need to align the type used to store engine ABI class and > instance. > > I did not find any other user visible inconsistency apart from the > tracepoints so I think importance of the fix is low. Alternatives: 1. Embed struct i915_engine_class_instance in struct intel_engine_cs, but downside is more churn. 2. Only tweak the tracepoints to cast back and forth, but is it possible to cast from unsigned to signed and get a negative number? 3. Do nothing, does anyone cares? Regards, Tvrtko > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > Cc: Chris Wilson <chris@chris-wilson.co.uk> > --- > drivers/gpu/drm/i915/gem/i915_gem_busy.c | 12 ++++++------ > drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++-- > 2 files changed, 8 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > index 3d4f5775a4ba..25235ef630c1 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c > +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > @@ -9,16 +9,16 @@ > #include "i915_gem_ioctls.h" > #include "i915_gem_object.h" > > -static __always_inline u32 __busy_read_flag(u8 id) > +static __always_inline u32 __busy_read_flag(u16 id) > { > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > + if (id == (u16)I915_ENGINE_CLASS_INVALID) > return 0xffff0000u; > > GEM_BUG_ON(id >= 16); > return 0x10000u << id; > } > > -static __always_inline u32 __busy_write_id(u8 id) > +static __always_inline u32 __busy_write_id(u16 id) > { > /* > * The uABI guarantees an active writer is also amongst the read > @@ -29,14 +29,14 @@ static __always_inline u32 __busy_write_id(u8 id) > * last_read - hence we always set both read and write busy for > * last_write. > */ > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > + if (id == (u16)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, u32 (*flag)(u8 id)) > +__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id)) > { > const struct i915_request *rq; > > @@ -57,7 +57,7 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) > return 0; > > /* Beware type-expansion follies! */ > - BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class)); > + BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class)); > return flag(rq->engine->uabi_class); > } > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h > index 00287515e7af..350da59e605b 100644 > --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h > +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h > @@ -278,8 +278,8 @@ struct intel_engine_cs { > u8 class; > u8 instance; > > - u8 uabi_class; > - u8 uabi_instance; > + u16 uabi_class; > + u16 uabi_instance; > > u32 uabi_capabilities; > u32 context_size; >
Quoting Tvrtko Ursulin (2020-01-15 15:28:19) > > On 15/01/2020 15:24, Tvrtko Ursulin wrote: > > From: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > > > > In our ABI we have defined I915_ENGINE_CLASS_INVALID_NONE and > > I915_ENGINE_CLASS_INVALID_VIRTUAL as negative values which creates > > implicit coupling with type widths used in, also ABI, struct > > i915_engine_class_instance. > > > > When for instance we export engine->uabi_class > > I915_ENGINE_CLASS_INVALID_VIRTUAL from our our tracepoints, because the > > type of the former is u8 in contrast to u16 defined in the ABI, 254 will > > be returned instead of 65534 which userspace would legitimately expect. > > > > Therefore we need to align the type used to store engine ABI class and > > instance. > > > > I did not find any other user visible inconsistency apart from the > > tracepoints so I think importance of the fix is low. > > Alternatives: > > 1. > Embed struct i915_engine_class_instance in struct intel_engine_cs, but > downside is more churn. Could do. It would seem to make sense. > 2. > Only tweak the tracepoints to cast back and forth, but is it possible to > cast from unsigned to signed and get a negative number? > > 3. > Do nothing, does anyone cares? It actually changes the value reported by GET_ENGINES for a virtual engine, right? engine->uabi_instance is u8, so u16 ci.engine_instance = engine->uabi_instance is zero extended, not sign extended. And we did say that is expected to be (u16)-2 already. So cc:stable > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > > Cc: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> > > --- > > drivers/gpu/drm/i915/gem/i915_gem_busy.c | 12 ++++++------ > > drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++-- > > 2 files changed, 8 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > index 3d4f5775a4ba..25235ef630c1 100644 > > --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c > > @@ -9,16 +9,16 @@ > > #include "i915_gem_ioctls.h" > > #include "i915_gem_object.h" > > > > -static __always_inline u32 __busy_read_flag(u8 id) > > +static __always_inline u32 __busy_read_flag(u16 id) > > { > > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > > + if (id == (u16)I915_ENGINE_CLASS_INVALID) > > return 0xffff0000u; > > > > GEM_BUG_ON(id >= 16); > > return 0x10000u << id; > > } > > > > -static __always_inline u32 __busy_write_id(u8 id) > > +static __always_inline u32 __busy_write_id(u16 id) > > { > > /* > > * The uABI guarantees an active writer is also amongst the read > > @@ -29,14 +29,14 @@ static __always_inline u32 __busy_write_id(u8 id) > > * last_read - hence we always set both read and write busy for > > * last_write. > > */ > > - if (id == (u8)I915_ENGINE_CLASS_INVALID) > > + if (id == (u16)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, u32 (*flag)(u8 id)) > > +__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id)) > > { > > const struct i915_request *rq; > > > > @@ -57,7 +57,7 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) > > return 0; > > > > /* Beware type-expansion follies! */ > > - BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class)); > > + BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class)); > > return flag(rq->engine->uabi_class); > > } > > > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h > > index 00287515e7af..350da59e605b 100644 > > --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h > > +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h > > @@ -278,8 +278,8 @@ struct intel_engine_cs { > > u8 class; > > u8 instance; > > > > - u8 uabi_class; > > - u8 uabi_instance; > > + u16 uabi_class; > > + u16 uabi_instance; Bah, doesn't this leave us with a u16 hole! -Chris
On 15/01/2020 15:35, Chris Wilson wrote: > Quoting Tvrtko Ursulin (2020-01-15 15:28:19) >> >> On 15/01/2020 15:24, Tvrtko Ursulin wrote: >>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com> >>> >>> In our ABI we have defined I915_ENGINE_CLASS_INVALID_NONE and >>> I915_ENGINE_CLASS_INVALID_VIRTUAL as negative values which creates >>> implicit coupling with type widths used in, also ABI, struct >>> i915_engine_class_instance. >>> >>> When for instance we export engine->uabi_class >>> I915_ENGINE_CLASS_INVALID_VIRTUAL from our our tracepoints, because the >>> type of the former is u8 in contrast to u16 defined in the ABI, 254 will >>> be returned instead of 65534 which userspace would legitimately expect. >>> >>> Therefore we need to align the type used to store engine ABI class and >>> instance. >>> >>> I did not find any other user visible inconsistency apart from the >>> tracepoints so I think importance of the fix is low. >> >> Alternatives: >> >> 1. >> Embed struct i915_engine_class_instance in struct intel_engine_cs, but >> downside is more churn. > > Could do. It would seem to make sense. > >> 2. >> Only tweak the tracepoints to cast back and forth, but is it possible to >> cast from unsigned to signed and get a negative number? >> >> 3. >> Do nothing, does anyone cares? > > It actually changes the value reported by GET_ENGINES for a virtual > engine, right? > > engine->uabi_instance is u8, so u16 ci.engine_instance = > engine->uabi_instance is zero extended, not sign extended. > > And we did say that is expected to be (u16)-2 already. > > So cc:stable You are correct, yep, was thinking about engine query where it doesn't apply but forgot about get_engines where it does. >>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> >>> Cc: Chris Wilson <chris@chris-wilson.co.uk> > Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> > >>> --- >>> drivers/gpu/drm/i915/gem/i915_gem_busy.c | 12 ++++++------ >>> drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++-- >>> 2 files changed, 8 insertions(+), 8 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> index 3d4f5775a4ba..25235ef630c1 100644 >>> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> @@ -9,16 +9,16 @@ >>> #include "i915_gem_ioctls.h" >>> #include "i915_gem_object.h" >>> >>> -static __always_inline u32 __busy_read_flag(u8 id) >>> +static __always_inline u32 __busy_read_flag(u16 id) >>> { >>> - if (id == (u8)I915_ENGINE_CLASS_INVALID) >>> + if (id == (u16)I915_ENGINE_CLASS_INVALID) >>> return 0xffff0000u; >>> >>> GEM_BUG_ON(id >= 16); >>> return 0x10000u << id; >>> } >>> >>> -static __always_inline u32 __busy_write_id(u8 id) >>> +static __always_inline u32 __busy_write_id(u16 id) >>> { >>> /* >>> * The uABI guarantees an active writer is also amongst the read >>> @@ -29,14 +29,14 @@ static __always_inline u32 __busy_write_id(u8 id) >>> * last_read - hence we always set both read and write busy for >>> * last_write. >>> */ >>> - if (id == (u8)I915_ENGINE_CLASS_INVALID) >>> + if (id == (u16)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, u32 (*flag)(u8 id)) >>> +__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id)) >>> { >>> const struct i915_request *rq; >>> >>> @@ -57,7 +57,7 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) >>> return 0; >>> >>> /* Beware type-expansion follies! */ >>> - BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class)); >>> + BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class)); >>> return flag(rq->engine->uabi_class); >>> } >>> >>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h >>> index 00287515e7af..350da59e605b 100644 >>> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h >>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h >>> @@ -278,8 +278,8 @@ struct intel_engine_cs { >>> u8 class; >>> u8 instance; >>> >>> - u8 uabi_class; >>> - u8 uabi_instance; >>> + u16 uabi_class; >>> + u16 uabi_instance; > > Bah, doesn't this leave us with a u16 hole! I don't see anything to fill it with. Could expand class and instance to u16 as well and see if it has any negative effect on code size. But in a separate patch. Regards, Tvrtko
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c index 3d4f5775a4ba..25235ef630c1 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c @@ -9,16 +9,16 @@ #include "i915_gem_ioctls.h" #include "i915_gem_object.h" -static __always_inline u32 __busy_read_flag(u8 id) +static __always_inline u32 __busy_read_flag(u16 id) { - if (id == (u8)I915_ENGINE_CLASS_INVALID) + if (id == (u16)I915_ENGINE_CLASS_INVALID) return 0xffff0000u; GEM_BUG_ON(id >= 16); return 0x10000u << id; } -static __always_inline u32 __busy_write_id(u8 id) +static __always_inline u32 __busy_write_id(u16 id) { /* * The uABI guarantees an active writer is also amongst the read @@ -29,14 +29,14 @@ static __always_inline u32 __busy_write_id(u8 id) * last_read - hence we always set both read and write busy for * last_write. */ - if (id == (u8)I915_ENGINE_CLASS_INVALID) + if (id == (u16)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, u32 (*flag)(u8 id)) +__busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u16 id)) { const struct i915_request *rq; @@ -57,7 +57,7 @@ __busy_set_if_active(const struct dma_fence *fence, u32 (*flag)(u8 id)) return 0; /* Beware type-expansion follies! */ - BUILD_BUG_ON(!typecheck(u8, rq->engine->uabi_class)); + BUILD_BUG_ON(!typecheck(u16, rq->engine->uabi_class)); return flag(rq->engine->uabi_class); } diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h index 00287515e7af..350da59e605b 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h @@ -278,8 +278,8 @@ struct intel_engine_cs { u8 class; u8 instance; - u8 uabi_class; - u8 uabi_instance; + u16 uabi_class; + u16 uabi_instance; u32 uabi_capabilities; u32 context_size;