[PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[Jiapeng Chong]

Eliminate the follow smatch warning:

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4640
guc_create_virtual() warn: assigning (-2) to unsigned variable
've->base.instance'.

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4641
guc_create_virtual() warn: assigning (-2) to unsigned variable
've->base.uabi_instance'.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index 36365bdbe1ee..dc7cc06c68e7 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -328,10 +328,10 @@ struct intel_engine_cs {
 	intel_engine_mask_t logical_mask;
 
 	u8 class;
-	u8 instance;
+	s8 instance;
 
 	u16 uabi_class;
-	u16 uabi_instance;
+	s16 uabi_instance;
 
 	u32 uabi_capabilities;
 	u32 context_size;
-- 
2.20.1.7.g153144c

Re: [PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[Jani Nikula]

On Wed, 16 Feb 2022, Jiapeng Chong <jiapeng.chong@linux.alibaba.com> wrote:
> Eliminate the follow smatch warning:
>
> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4640
> guc_create_virtual() warn: assigning (-2) to unsigned variable
> 've->base.instance'.
>
> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4641
> guc_create_virtual() warn: assigning (-2) to unsigned variable
> 've->base.uabi_instance'.
>
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

The report seems to be valid, but I don't think this is the fix.

Where do we even check for invalid instance/uabi_instance in code?

BR,
Jani.


> ---
>  drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> index 36365bdbe1ee..dc7cc06c68e7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> @@ -328,10 +328,10 @@ struct intel_engine_cs {
>  	intel_engine_mask_t logical_mask;
>  
>  	u8 class;
> -	u8 instance;
> +	s8 instance;
>  
>  	u16 uabi_class;
> -	u16 uabi_instance;
> +	s16 uabi_instance;
>  
>  	u32 uabi_capabilities;
>  	u32 context_size;

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[Ville Syrjälä]

On Wed, Feb 16, 2022 at 11:02:06AM +0200, Jani Nikula wrote:
> On Wed, 16 Feb 2022, Jiapeng Chong <jiapeng.chong@linux.alibaba.com> wrote:
> > Eliminate the follow smatch warning:
> >
> > drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4640
> > guc_create_virtual() warn: assigning (-2) to unsigned variable
> > 've->base.instance'.
> >
> > drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4641
> > guc_create_virtual() warn: assigning (-2) to unsigned variable
> > 've->base.uabi_instance'.
> >
> > Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> > Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> 
> The report seems to be valid, but I don't think this is the fix.
> 
> Where do we even check for invalid instance/uabi_instance in code?

The whole thing seems rather poorly documented as there's a matching
uabi struct with __u16's and the negative values are defined right
there in the uapi header as well.

> 
> BR,
> Jani.
> 
> 
> > ---
> >  drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > index 36365bdbe1ee..dc7cc06c68e7 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > @@ -328,10 +328,10 @@ struct intel_engine_cs {
> >  	intel_engine_mask_t logical_mask;
> >  
> >  	u8 class;
> > -	u8 instance;
> > +	s8 instance;
> >  
> >  	u16 uabi_class;
> > -	u16 uabi_instance;
> > +	s16 uabi_instance;
> >  
> >  	u32 uabi_capabilities;
> >  	u32 context_size;
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

-- 
Ville Syrjälä
Intel

Re: [PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[Tvrtko Ursulin]

On 16/02/2022 09:19, Ville Syrjälä wrote:
> On Wed, Feb 16, 2022 at 11:02:06AM +0200, Jani Nikula wrote:
>> On Wed, 16 Feb 2022, Jiapeng Chong <jiapeng.chong@linux.alibaba.com> wrote:
>>> Eliminate the follow smatch warning:
>>>
>>> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4640
>>> guc_create_virtual() warn: assigning (-2) to unsigned variable
>>> 've->base.instance'.
>>>
>>> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4641
>>> guc_create_virtual() warn: assigning (-2) to unsigned variable
>>> 've->base.uabi_instance'.
>>>
>>> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
>>> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
>>
>> The report seems to be valid, but I don't think this is the fix.
>>
>> Where do we even check for invalid instance/uabi_instance in code?
> 
> The whole thing seems rather poorly documented as there's a matching
> uabi struct with __u16's and the negative values are defined right
> there in the uapi header as well.

Negative ones are exception values to be used in conjunction with the virtual engine uapi (see "DOC: Virtual Engine uAPI" and also comment next to I915_CONTEXT_PARAM_ENGINES).

AFAIK assigning negative int to unsigned int is defined and fine.

Compiler does warn on comparisons which is why we have:

./gem/i915_gem_busy.c:  if (id == (u16)I915_ENGINE_CLASS_INVALID)
./gem/i915_gem_busy.c:  if (id == (u16)I915_ENGINE_CLASS_INVALID)
./gem/i915_gem_context.c:               if (ci.engine_class == (u16)I915_ENGINE_CLASS_INVALID &&
./gem/i915_gem_context.c:                   ci.engine_instance == (u16)I915_ENGINE_CLASS_INVALID_NONE)

So I think no action needed here.

Regards,

Tvrtko
  
>>
>> BR,
>> Jani.
>>
>>
>>> ---
>>>   drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>> index 36365bdbe1ee..dc7cc06c68e7 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>> @@ -328,10 +328,10 @@ struct intel_engine_cs {
>>>   	intel_engine_mask_t logical_mask;
>>>   
>>>   	u8 class;
>>> -	u8 instance;
>>> +	s8 instance;
>>>   
>>>   	u16 uabi_class;
>>> -	u16 uabi_instance;
>>> +	s16 uabi_instance;
>>>   
>>>   	u32 uabi_capabilities;
>>>   	u32 context_size;
>>
>> -- 
>> Jani Nikula, Intel Open Source Graphics Center
> 

Re: [PATCH] drm/i915/gt: fix unsigned integer to signed assignment

[Jani Nikula]

On Wed, 16 Feb 2022, Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com> wrote:
> On 16/02/2022 09:19, Ville Syrjälä wrote:
>> On Wed, Feb 16, 2022 at 11:02:06AM +0200, Jani Nikula wrote:
>>> On Wed, 16 Feb 2022, Jiapeng Chong <jiapeng.chong@linux.alibaba.com> wrote:
>>>> Eliminate the follow smatch warning:
>>>>
>>>> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4640
>>>> guc_create_virtual() warn: assigning (-2) to unsigned variable
>>>> 've->base.instance'.
>>>>
>>>> drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c:4641
>>>> guc_create_virtual() warn: assigning (-2) to unsigned variable
>>>> 've->base.uabi_instance'.
>>>>
>>>> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
>>>> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
>>>
>>> The report seems to be valid, but I don't think this is the fix.
>>>
>>> Where do we even check for invalid instance/uabi_instance in code?
>> 
>> The whole thing seems rather poorly documented as there's a matching
>> uabi struct with __u16's and the negative values are defined right
>> there in the uapi header as well.
>
> Negative ones are exception values to be used in conjunction with the virtual engine uapi (see "DOC: Virtual Engine uAPI" and also comment next to I915_CONTEXT_PARAM_ENGINES).
>
> AFAIK assigning negative int to unsigned int is defined and fine.
>
> Compiler does warn on comparisons which is why we have:
>
> ./gem/i915_gem_busy.c:  if (id == (u16)I915_ENGINE_CLASS_INVALID)
> ./gem/i915_gem_busy.c:  if (id == (u16)I915_ENGINE_CLASS_INVALID)
> ./gem/i915_gem_context.c:               if (ci.engine_class == (u16)I915_ENGINE_CLASS_INVALID &&
> ./gem/i915_gem_context.c:                   ci.engine_instance == (u16)I915_ENGINE_CLASS_INVALID_NONE)
>
> So I think no action needed here.

We never check instance or uabi_instance members against
I915_ENGINE_CLASS_INVALID_VIRTUAL anywhere.

BR,
Jani.

>
> Regards,
>
> Tvrtko
>   
>>>
>>> BR,
>>> Jani.
>>>
>>>
>>>> ---
>>>>   drivers/gpu/drm/i915/gt/intel_engine_types.h | 4 ++--
>>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>>> index 36365bdbe1ee..dc7cc06c68e7 100644
>>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
>>>> @@ -328,10 +328,10 @@ struct intel_engine_cs {
>>>>   	intel_engine_mask_t logical_mask;
>>>>   
>>>>   	u8 class;
>>>> -	u8 instance;
>>>> +	s8 instance;
>>>>   
>>>>   	u16 uabi_class;
>>>> -	u16 uabi_instance;
>>>> +	s16 uabi_instance;
>>>>   
>>>>   	u32 uabi_capabilities;
>>>>   	u32 context_size;
>>>
>>> -- 
>>> Jani Nikula, Intel Open Source Graphics Center
>> 

-- 
Jani Nikula, Intel Open Source Graphics Center